Is 'physical modelling' set to become the buzz‑phrase of '90s synthesis? Martin Russ exclusively tests out Yamaha's innovative new synth and reveals all...
"But it looks like the dashboard of a Morris Minor!" gasped my wife, as I unpacked the VL1. The combination of claro walnut panels and gold‑coloured plastic is presumably intended to look expensive, but I am not entirely sure if Japanese design has captured the right image here. However, what an instrument looks like is very secondary to how it sounds and how it plays, and this is where the new Yamaha VL1 'Virtual Acoustic' synthesizer attempts to break new ground. Genuine breakthroughs happen all too rarely in the field of synthesis, and the rumours which preceded the arrival of this instrument grew almost to fever pitch, so what is it actually like?
The VL1 is almost like a return to the world of two decades ago, when if you wanted a synthesizer you bought a MiniMoog. It is hard now to appreciate just how astonishing a 'Mini' sounded to ears accustomed to electric pianos and organs, but it had a reputation for being expensive and very difficult to master — and yet, the Moog's sound sold it. The whole idea of introducing what is really a monophonic synthesizer into today's polyphonic world takes a very confident company, and I think it may well pay off for Yamaha in this case. The VL1 is not just another synthesizer. It represents a major change in the way that electronic musical instruments are made and perceived. It really is that different!
The VL1 is not just another synthesizer. It represents a major change in the way that electronic musical instruments are made and perceived. It really is that different!
We are talking sounds here. There are no samples, no function generators, and much less use of envelopes and filtering — and yet, despite throwing away almost everything with which you may be familiar, the VL1 produces sounds which feel so much like real instruments that it is hard to think of them as electronically generated. The secret involves what is called 'physical modelling', although there is nothing physical about the Digital Signal Processing inside a VL1!
What Yamaha have done is exploit their intimate knowledge of real instruments by creating a mathematical model of how some instruments work. Instead of the usual approach employed by many Sample & Synthesis (S&S) instruments like the Roland D50 and Korg M1, where a basic sampled sound waveform is modified by a filter and envelopes to produce a finished sound, the VL1 uses its internal model of an instrument to create the whole sound — in one operation. Because the model encompasses the entire instrument, it behaves like the actual thing, and so it also produces realistic transitions between notes, not just the notes themselves.
Playing It
The first thing most people want to do with any new instrument is to play it. The VL1 manual encourages the use of lots of MIDI Controllers, and a BC2 Breath Controller and FC7 Foot Controller Pedal are both included, so you really have no excuse not to use them. The BC2 is a marked improvement over the BC1 [which came with the original DX7 back in 1983] — it looks much more like a microphone headset and is much easier to use. I fell in love with it almost immediately.
Yamaha VL1 with its BC1 breath controller headset.
Those same words apply to the VL1 itself. I must admit to being somewhat sceptical before it arrived, mainly because I had heard on the grapevine that the 'physical modelling' instruments used in research were very limited and rather unimpressive. However, the VL1 was different. My first 'commercial' synthesizer purchase was a Sequential Circuits Pro‑One, with which I spent my formative years mastering the techniques of wheel pulling, highest‑note priority trills, and all the other tricks of the monophonic synth soloist's art. So I was certainly ready to try out this unusual looking monophonic synthesizer. What I was not prepared for was the stunning sense of realism that the VL1 exudes.
On certain factory patches, moving the Pitch Wheel starts to nudge the pitch, which then dies away and you find a harmonic will start up — then you realise that it is playing the harmonic overtone series that you get with a real brass instrument. On other patches, you can produce all sorts of interesting instabilities if you blow too hard with the Breath Controller. Blowing softly can make the breath noise gradually grow more and more resonant, until a pitched note locks into place. Even with those VL1 patches which do not attempt to emulate a real‑world instrument, you still get the feeling that you are interacting with a musical instrument — and this was quite a revelation to me!
I asked a trombone player to listen to a few of the brass sounds I was playing, and his eyebrows raised when I showed him the effects of changing the embouchure (lip pressure) with the Modulation Wheel — when you can add those characteristic brassy bursts of noise and sound that coalesce into the following note, then you begin to realise how limited conventional S&S instruments can be in comparison to the VL1.
Instrument Definitions
The actual instrument definitions used on the VL1 can be so complicated that Yamaha have chosen to make them factory‑defined only. To compensate for this, they have provided lots of user control over the sound, and a comprehensive set of modifiers and effects which process the output of the instrument. You can also load in new instruments from disk, via the floppy drive — Yamaha are releasing several support disks for the VL1, and no doubt third party disks will eventually be released also. As it comes, you can map any MIDI Controller to any of the following available instrument controls:
- Pressure (or bow speed)
- Embouchure (tightness of lips or bow pressure on the string)
- Pitch (the length of the tube or string)
- Vibrato (affects Pitch or Embouchure via an LFO)
- Tonguing (simulates half‑tonguing damping of saxophone reed)
- Amplitude (controls volume without changing the timbre)
- Scream (drives the whole instrument into chaotic oscillation)
- Breath Noise (adds widely variable breath sound)
- Growl (affects Pressure via an LFO)
- Throat Formant (simulates the player's lungs, throat and mouth)
- Dynamic Filter (controls the cutoff frequency of the Modifier Filter)
- Harmonic Enhancer (changes the harmonic structure of the sound)
- Damping (simulates air friction in the tube or on the string)
- Absorption (simulates high frequency loss at the end of the tube or string)
As you can see, most of these Controllers are very specific to real instruments — even instruments that don't and can't exist! Although you can't get at the instrument definition directly, all these controls require more parameters than you might expect — almost a thousand, in fact (the MIDI Sysex is formidable). There are individual scaling curves and offsets for each controlled parameter, so you can adjust the effect of a Controller like Breath Control to make it achieve exactly what you want, with great precision.
...the VL1 produces sounds which feel so much like real instruments that it is hard to think of them as being electronically generated.
The Modifiers are all designed to let the user manipulate the sound produced by the basic instrument model. For example, the Harmonic Enhancer is effectively a 2‑operator FM section, where you can process the instrument sound and add extra harmonics in much the same way as using RCM on a Yamaha SY77 or SY99. The Dynamic Filter is probably the most conventional part of the whole VL1, although it has a few extra parameters. The Equaliser is a 5‑band parametric EQ, with shelving high and low pass filters, as well as key scaling on many of the values — this eases the setting up of detailed ranges and responses. The Impulse Expander is a variation on an early reflection effect, but it uses a frequency‑dependent delay so that the overall process simulates a resonant cavity or sound box (such as the body of an acoustic guitar), and it has a characteristic metallic quality. The Resonator uses five time delays in parallel to generate a more woody‑sounding resonant effect.
The VL1's on‑board Effects offer the usual selection of modulation, echo and reverberation treatments, with the addition of distortion. A Virtual Acoustics‑specific [see side box] DSP chip is used to produce these effects, but unlike most conventional instruments, you can also use MIDI Controllers to change some of the Effects parameters — so you could vary the flanger's LFO frequency using the Breath Controller, if you wished. The VL1 also offers micro‑tuning facilities, and the possibilities provided by mapping pitch to breath pressure or embouchure mean that you can perform fine adjustments to pitch as part of your normal playing. The depth of expression provided by all these Controllers really has to be experienced before it can be fully appreciated.
Having edited the Controllers, Modifiers and Effects, you can then save your edited sound into any of the 128 memories, and save it to disk too. Yamaha have deliberately provided a wide range of basic 'instruments' which you can then customise to your own tastes and save. Having two Elements (instruments) available at once also opens up possibilities for layering and detuning.
It has to be said that the VL1's page‑based operating system is a little poor in its use of graphics — the envelopes, for instance, are shown only as numbers. I would also like to register my complaint about the disk drive system, which always fills the first available RAM memories when you load more than one sound at once.
Yamaha VL1 element, effect and modifier selector buttons.
Exterior Decor
The VL1 has a four‑octave keyboard which produces polyphonic MIDI Note messages from the MIDI Out socket on its rear panel, even though the majority of patches are monophonic, with only a few duophonic.
The styling follows on from the SY77 and SY99, rather than the SY35 and SY85, and delivers the same mix of assignable softkeys below the LCD display, patch selection buttons which double up as editing buttons on the right; cursor movement buttons and data wheel to the right of the display; with slider and mode buttons on the left side. No surprises here, although the fluorescent backlit LCD offers just about the best contrast and brightness I have ever seen — I suspect that it is an active matrix type rather than the more usual passive matrix displays.
Yamaha's usual three wheels now sport the increasingly fashionable (and very effective) rubber coating, which helps your fingers maintain a grip even in the most testing of playing conditions. A floppy disk drive is hidden away on the left‑hand side, underneath the gold plastic top surface. You need to grope about with your fingers to get at the disk, because you can't see what is happening without contorting your head around and underneath. As such, the disk drive looks very much like an afterthought rather than an integral part of the design. The keyboard itself feels very similar to the SY99 or SY77, with a light touch and no rough edges to catch on your fingers. But overall, the VL1 gives off the feel of a high quality instrument.
The Inside Story
Inside the VL1 case, there is a single main processing printed circuit board (PCB) crammed on both sides with silicon chips, many of them custom LSIs made by Yamaha. This 'processing' PCB is 380 x 140 mm, and uses double‑sided surface mount technology — so the component pins are held onto the pads by the solder, rather than passing through the board.
One side holds the Yamaha chips: four YSS217Bs, two XM272AOs and one XM234AO, along with three Toshiba 68301 processors, two EPROMs containing the operating system software, and a NatSemi ADC chip for all the controllers — the ADC0809. The other side of the board features 20 RAM chips, which suggests that S/VA synthesis uses large quantities of memory. The rest of the board houses a lot of miscellaneous TTL logic chips: AS, ALS and HC varieties. The static RAM voice storage has a large battery for backup purposes.
Techniques and algorithms for modelling musical instruments have only recently begun to reach the level of sophistication where they can be implemented in real time (using DSP technology) without the aid of rooms full of super‑computers...
The power supply uses switch mode technology with a total power dissipation of only 16 Watts — some slots in the base of the casing provide enough air‑flow to keep it cool. Hidden away underneath the disk drive is the Digital to Analogue Conversion board, which uses two Burr‑Brown 16 times oversampling 20‑bit PCM1702 DAC chips to produce the audio output. The PCM1702 is designed for ultra‑low distortion and incorporates an advanced complementary linear architecture that eliminates unwanted glitches and other non‑linearities around bipolar zero volts, giving an audio performance intended for professional digital audio applications.
Conclusion
What can I say? I can't afford one; I haven't got the time to learn how to play it properly; and yet this is one of the most desirable instruments I have ever heard. I can see some session players earning lots of money from the VL1 — and that is probably where it sits in the market: for serious professionals only. The rest of us can sit and bite our fingernails hoping that a more affordable version does not appear to tempt us (but it probably will, eventually)!
Curiously, exactly the same strengths that make Emu's new Morpheus synthesizer a powerful and expressive tool also apply to the VL1, despite the synthesis methods being so different. Both products require careful and detailed use of MIDI Controllers, and lose much of their appeal if played only from the keyboard using just velocity control. They each offer synthesis systems of sufficient complexity to stretch the programming capability of their owners, and neither depends on raw samples for how they sound — the VL1 even more so than the Morpheus. More importantly, the comprehensive and responsive expression facilities offered by the VL1 mean that this is another instrument that you won't be able to sample easily without losing everything about it that makes it sound so special. The future does not lie with larger ROM samples and ever more cliched sample sets, or even SCSI‑connected CD‑ROMs of prepackaged sounds; it lies with synthesis, and I put the Yamaha VL1 in pole position.
Physical Modelling: The Key To Realism
'Virtual Acoustics' is Yamaha's wording for what academics call Physical Modelling (PM), where you use mathematics to try and describe something in enough detail that you can predict how the real thing would behave. Techniques and algorithms for modelling musical instruments have only recently begun to reach the level of sophistication where they can be implemented in real time (using DSP technology) without the aid of rooms full of super‑computers, and the Yamaha VL1 arguably represents the same sort of technological leap that the GS1/DX7 provided a decade ago, when analogue synthesizers were replaced by FM‑based digital machines almost at a stroke.
Using maths to make models of real world objects sounds a little strange, so let's have a look at a simple example. Imagine a tap and a bucket with a hole in it. If we make some measurements we can quickly find out that the tap can provide anything up to 10 litres of water per minute, the bucket holds 20 litres, and that the hole leaks at the rate of 1 litre per minute. If we ignore the leak, then we can estimate that the fastest time taken to 'fill' the bucket by the tap (when fully on) is the time it takes for the tap to provide 20 litres of water, which would be two minutes. (That's 20 litres at 10 litres per minute = 2 minutes.)
Now let's consider what effect the hole will have. In the first minute, one litre of water will escape out of the hole, and so only nine out of the 10 litres supplied by the tap will be in the bucket at the end of the first minute. During the second minute another litre of water leaks away and so there will only be 18 litres in the bucket. Therefore it will obviously take slightly longer than the original estimate of two minutes to fill the bucket, because we still need to provide just over two more litres of water...
There are quite a few other things that we can figure out about our 'tap and bucket with hole' model. For example, if we turn on the tap so that it supplies less than one litre of water per minute, then the bucket will never fill up because the hole leaks at a rate of one litre per minute. We also know that when we have put 20 litres into the bucket, then it will begin to overflow — and if you subtract the one litre per minute leak, then the overflow rate is the tap supply rate (from just over one to 10 litres per minute) minus the leak rate. So, with the tap fully on, the bucket will overflow after just over two minutes have passed, and the overflow rate will be nine litres per minute.
As you can see, with a few simple calculations like these we can make some quite complex predictions about the way that the real world works. Yamaha's model of how musical instruments work is obviously more complex than our water example, but it is based on the same principles — you measure what happens, produce a description of what is happening, and then you use this information to work out what will happen.
S/VA SYNTHESIS
In the case of the VL1, Yamaha have produced mathematical models of the two major parts of most blown/bowed musical instruments: (1) the bit that you blow or move; and (2) the part that vibrates. They call this Self‑oscillating Virtual Acoustic (S/VA) synthesis.
In a reed instrument, you blow into a mouthpiece, whilst for a trumpet your lips move and control the flow of air. For a stringed instrument, the bow scrapes across the string. With all of these, you are forcing the instrument to make a sound — and so these aspects are called Drivers. In contrast, the air inside a saxophone or trumpet vibrates inside a tube and so creates a sound, or the string vibrates and moves the air around to generate a sound, and these make up the Pipe or String part of the model. Whereas in a real instrument you tend to have fixed combinations of drivers and pipes or strings, in the VL1 you can have any mix you like. So a reed type of driver feeding into a string is entirely possible, even though there is no real world equivalent!
As you can probably imagine, trying to describe enough about an instrument to be able to figure out how it works is going to be a complex task. Yamaha do not give any direct user control over the instrument in the VL1, but instead provide a large number of predefined instruments which can then be controlled and modified by the player. Although this goes against the grain of most previous synthesizers, it is exactly how real instruments work — you do not take a drill to a saxophone and try making holes in the metalwork! Instead, you use the mouthpiece to control the sound through a combination of air pressure, lip pressure, throat resonance, vocal chords and your tongue. Given Yamaha's long experience of making musical instruments, the models are complex enough to provide exactly the sort of subtle and expressive control over timbre and pitch that you would expect from a real instrument. And judging by the instruments provided by the disks released so far for the VL1, there is quite a lot of scope for modelling a wide range of instruments too.
Controlling the instruments provided by the VL1 requires some way to emulate the many different playing controls that various real instruments have. Blowing can be easily simulated by using the BC2 Breath Controller, but lip or bow pressure, muting or string damping are less obviously created, and so foot controllers, key velocity and aftertouch can be used, although it requires a great deal of practice to recreate the characteristic playing nuances of various instruments. The important thing to remember is that you will need to 'play' a VL1 — it is not just a question of pressing a few notes on the keyboard. I'm afraid that this is one instrument where practice really is essential.
Influences?
Yamaha are being very protective of the technology employed inside the VL1. Apart from saying that custom Yamaha DSP chips are involved, and that physical modelling based upon Julius O. Smith's work (licensed from Stanford University) is used, no other details were made available to me during the review period. But a search through the literature on physical modelling, from serious academic research, produced a few interesting papers which may well have influenced the Yamaha engineers:
- Julius O. Smith III, 'Physical Modelling using Digital Waveguides', Computer Music Journal, Vol 16, Number 4, Winter 1992.
- Julius O. Smith III, 'Musical Applications of Digital Waveguides', Stanford University Center for Computer Research in Music and Acoustics, STAN‑M‑39.
- Charles R. Sullivan, 'Extending the Karplus‑Strong Algorithm to Synthesize Electric Guitar Timbres with Distortion and Feedback', Computer Music Journal, Vol 14, Number 3, Fall 1990.
- Perry R. Cook, 'SPASM, a Real‑Time Vocal Tract Physical Model Controller', Computer Music Journal, Vol 17, Number 1, Spring 1993.
- Karplus, K. and A. Strong, 'Digital Synthesis of Plucked String and Drum Timbres', Computer Music Journal, Vol 7, Number 2, Summer 1983.
- Douglas H. Keefe, 'Physical Modelling of Wind Instruments', Computer Music Journal, Vol 16, Number 4, Winter 1992.
Many of these papers are quite technical, so if phrases like 'a set of three first‑order coupled, non‑linear differential equations' or 'a fricative consonant' mean absolutely nothing to you, then don't look them up! Most of these papers suggest that real‑time physical modelling is possible using DSP technology, but at least one paper comments that there are only good models for a limited number of real instruments. Digital waveguides crop up several times, and seem to be a very computationally efficient way of simulating a pipe or string, and probably form part of the VL1 technology, whilst a variation on the 'Karplus‑Strong' plucked string algorithm might well be the inspiration for the VP1.
The Computer Music Journal, from which these papers emanate, is a good source of information on the 'state‑of‑the‑art' in academic music research. It is published quarterly by the MIT Press, Fitzroy House, 11 Chenies Street, London WC1E 7ET. Telephone 071 306 0603. Fax 071 306 0604.
VL1 Specification
- 49 key, C‑to‑C, keyboard with Velocity and Channel Aftertouch sensitivity
- Pitch Bend, Modulation, Assignable Wheels
- Octave shift up/down buttons
- 2 Continuous Slider controls
- Breath Controller input
- 2 Foot Controller Pedal inputs
- Data Entry Wheel
- Synthesis method: Self‑oscillating Virtual Acoustic (S/VA) synthesis. Voice made up from 1 or 2 separate Elements.
- Modifiers: Harmonic Enhancer, Resonant Dynamic Filter (Low‑pass, High‑pass, Band‑pass & Notch), 5‑band Parametric Equaliser, Impulse Expander, Resonator.
- Built‑in S/VA‑specific Effects processor (32‑bit DSP, stereo in/out): Modulation (flanger, pitch change, chorus), Delay (Echo), Reverberation, Distortion.
- Polyphony: 2 notes maximum.
- Internal RAM storage: 128 voices.
- External Storage: 3.5 inch DD / HD disk drive.
- 240 x 64 dot backlit LCD
- Output Level: Stereo, 2.5 +/‑ 2 dBm into 10k Ohms.
- Dynamic Range: Not available (but uses two 20‑bit DACs).
- MIDI Response Time: Measured at 5 +/‑ 0.5 milliseconds
VL1 Data Files
The VL1 uses a LOT of storage for each of its patches ('voices' in Yamaha‑speak) — the FACTORY_ALL file on the supplied disk contains 128 patches and occupies 387 kBytes, which is roughly 3,000 bytes per patch. In comparison, a DX7 FM patch uses only 155 bytes, and only 128 bytes in its compressed form! Even so, the size of the file is still tiny when compared to that of a sampled sound in a typical S&S synthesizer (D50, M1, SY77 etc), where about 88 kBytes of storage are required for each second's worth of sample.
MIDI Control
The depth of control required to draw the most out of the VL1's S/VA synthesis employs the whole spectrum of available MIDI Controller devices. Unusually, Yamaha's demonstration sequences within the VL1 also appear at the MIDI Out socket, and so I captured these in my sequencer and then dissected out the Controllers that are used. The screenshot shows what's going on.
What The Players Say
As you might expect, the VL1 is already selling to professional musicians. We managed to get a few words from some of the more famous — including synth‑pop sorcerer Howard Jones, and Conductor of the Masses himself...
- JEAN‑MICHEL JARRE
"I like very much the idea of having created a sophisticated solo synthesizer. With the VL1, I think that we have entered the science fiction of musical instruments. I wish that we will be given the way to create our models of virtual instruments ourselves. I would also like to see new kinds of controllers to act on the expression parameters in a more rational way than using a piano keyboard, breath controller and modulation wheel." - MICHEL GEISS (Instrument Designer and M. Jarre's keyboard technician/collaborator)
"Beyond the technology achievement of an affordable physical modelling instrument, the VL1 is a very musical instrument. The musician's expression is far more meaningful than on most of the other synthesizers, simply because the VL1 reacts to the player as an acoustic instrument, with all the behaviour attached to it. Now that we have proof that virtual acoustics works, I am waiting for more new imaginary instruments that would sound quite differently than real‑world ones. In that way, I cannot wait to use the VL1 as a solo instrument in new compositions." - HOWARD JONES
"The VL1 is the most exciting synth I have had the pleasure of getting my mitts on for years. It takes me back to the memories of recieiving my first synth (Moog Prodigy) and the thrill of a chance encounter with a CS80, complete with ribbon controller. Put it this way: if the VL1 was a car, it would definitely be a Ferrari. This is a synth that feels like a real instrument — it is a keyboard for soloists. Every time you play a note the sound has subtly altered, and with a pitch controller and two modulation wheels, aftertouch, and the essential breath controller, you feel as though you really are connected to the sound production. This hi‑tech little beauty can feel like ethnic instruments, with all the organic scrapes, detunes and mis‑blowing that give these sounds their real character, and then, chameleon‑like, change into some ferocious 21st century nightmare deathsynth with filters firing on full power, captain. If this is the way synthesis is going to go then I will heartily raise a cheer, because it brings expression with a capital E to the fingertips of contemporary keyboarders."
'Nuff said!
And What's Next?
If you think that the VL1 is expensive, then don't even consider the VP1, with a price tag rumoured to be closer to £10,000. Whereas the VL1's S/VA synthesis is designed to synthesize real monophonic instruments, the VP1 is intended to produce polyphonic synthetic timbres, and uses a different variation of physical modelling called 'Free‑oscillation Virtual Acoustics' (and probably based on the Karplus‑Strong algorithm for producing plucked and struck sounds). The VP1 is due out later this year.
Since the VL1 and VP1 don't use the same method of sound production, it seems unlikely that a composite of the two will be produced, since this would be uneconomic. The current split into 'solo' and 'accompaniment' instruments actually makes a great deal of sense — after all, real world instruments naturally divide into monophonic solo instruments (eg. trumpet) and polyphonic accompaniment ones (eg. piano).
If Yamaha are following their usual trend, then these instruments may be the first members of a new family. The costly and rare GS1 preceded the affordable and best‑selling DX7, giving an enticing glimpse of what was to come. Yamaha are keeping tight‑lipped about the possibility of low cost future Virtual Acoustics releases, and the VL1 does have a very finished feel to it, with a lot of new sounds already becoming available for it on disk. Perhaps the era of ever‑falling prices of synthesizers has come to an end [see Waldorf Wave review elsewhere in this issue] — after all, in 1978, a Prophet 5 cost about half of an average year's wage to buy. And of course, price does buy exclusivity!
Physical Modelling technology does seem to be appearing in a range of new products: Korg have licensed the Yamaha LSI technology for producing percussive Virtual Acoustic synthesis sounds, and MediaVision have just announced a PC card which utilises Physical Modelling.
Pros
- Expressive, astonishingly 'real' feeling instrument sounds, even the synthetic ones.
- Highly customisable presets.
- Not a replacement for real instruments, more a whole new set of them!
Cons
- Cost.
- Lots to learn and lots of parameters to tweak = time & practice required.
- Does S/VA synthesis have power to 'model' a wide enough range of instruments?
Summary
Digital Signal Processing technology enters a new phase of development. Synthesis will never be the same again. The death‑knell for 'Sample & Synthesis' instruments?