Sonic Foundry Acid

The Acid window, showing the three main areas: the main pattern‑based Track View, the Track List to its left, and the Media Explorer, mixer and effects section beneath.

Loop‑based sequencing can involve heavy‑duty time‑stretching and pitch‑shifting, but Sonic Foundry aim to change this with Acid, which allows you to mix multiple sample loops while changing their pitch and tempo in real time. Martin Walker applies the Acid test.

When you get asked to try acid at a music show, you tend to be wary. But thankfully, the only mind‑expanding substance at the Frankfurt launch of Sonic Foundry's new PC software was a cheese buffet! Acid is described as a "breakthrough loop‑based music production tool", and the emphasis is on creative flexibility and instant results. Supplied with a huge selection of style‑based WAV loops and single‑shot sounds, you can drag and drop snippets of audio on to a version of the Arrange page already familiar to Cubase users.

The clever bit is that Acid allows real‑time changes to pitch or tempo, so that you can alter the tempo of a whole clutch of different loops to run in sync, simply by moving a bpm slider. You can also change their pitch to create a song structure, while extensive editing options allow you to move, snap to grid, loop and otherwise manipulate your source material, all with unlimited levels of undo/redo. As you might expect, Acid is compatible with Sound Forge for more extensive editing, and CD Architect if you want to burn a CD of your performance. Acid will run on a Pentium 133 machine, although you can also take advantage of DirectX real‑time effects if you have a Pentium II processor.

Installation

Opening up the Properties section allows you to tweak the track sample for optimum results. Here the Stretch page shows the markers that are used when time compressing and expanding.

During the installation, you are given the option of installing the latest DirectX Media 5.2a Streaming files, so I opted to do this. Unfortunately, my PC locked up during the procedure, although thankfully nothing seemed untoward after a reboot, apart from several discarded temporary files. Running setup.exe on the CD‑ROM a second time produced the familiar Sonic Foundry install page, and after entering the serial number to activate the program, Acid was soon up and running.

Apart from the program files, the CD‑ROM contains more than 500 loops and other sounds ready for use, including tasters from a variety of other manufacturers' libraries. To speed up loading times you can transfer these to your hard drive, but they can be used directly from the CD‑ROM without any real‑time performance penalty, since they are normally held in RAM for playback. Acid can load in any WAV or AIFF‑format samples, as well as its own ACD (Acid project) files.

Sonic Foundry are to be congratulated on a well‑written user interface. I found I had loaded up a bunch of WAV files and had written a song before I even glanced at the manual — it's that easy to use.

There are three types of tracks: Loops, One‑Shot, and Disk‑Based. The most commonly used are likely to be Loops, which, because they are repeated, are held in RAM for faster access. Unlike many other programs, the core engine of Acid provides real‑time tempo and pitch adjustment, so that any loop can be stretched or squashed to fit the current project. One‑Shots, as the name suggests, are normally shorter snippets of sound which are played once, in their entirety. Again these are held in RAM, but, unlike loops, their tempo remains fixed. One‑Shots are therefore ideal for incidental sounds like cymbal crashes. For longer chunks of audio that don't need looping (such as vocal lines), Disk‑Based tracks are played directly from the hard disk, but can still be time‑stretched if required to suit the project.

Although Acid is a sequencer, there is a fundamental difference compared to a traditional multitrack MIDI or Audio sequencer, in that each file you load creates and occupies a single track (whether it be Loop, One‑Shot, or Disk‑Based). This makes it much more like a sophisticated drum‑based pattern editor.

Panes And Pleasure

Once you zoom in on the track waveforms it is easier to draw in automation of volume, pan, and the level of the DirectX effect busses. (Here FX1 is currently using the TC Works Native Essential reverb, shown in the effect pages at the bottom of the screen.)

The main display window (see page 176) is divided into three main areas: the Track View, its associated Track List to the left, and the Multi‑Function section at the bottom (which we'll come back to later). Much of the creative work happens in the Track View, where it is easy to see your arrangement at a glance. It is normally the largest part of the screen, although you can drag the divisions between the window sections to change the size of any portion to taste. There are also both horizontal and vertical scrollbars with zoom controls (these are identical to those of Sound Forge, as are the keyboard shortcut commands).

Along the top is the Beat Ruler, which displays bars and beats. These divisions also appear in the Track View background as a grid, which is very useful when lining up Events (Sonic Foundry's name for any item that appears in a track). Normally the Events will snap to the Ruler marks, but you can also choose any snap value between whole notes and sixty‑fourth notes, as well as disabling it altogether. Along the bottom of the Track View is the Time Ruler with options to display this as Samples, Time, or SMPTE. The lower half of the ruler allows tempo or key changes to be inserted freely at any point (see screenshot on page 180), a feature which overcomes the normal rigidity of the pattern‑based approach.

If Acid had been released a few months ago it would probably have wiped the field, but now it is not without competition.

The Track List contains the master controls for each track. On show are the track type and name and three small icons for selecting Mute, Solo, and the playback device (note that you can send individual tracks to different outputs if your soundcard has them). There are also four draggable faders, although only one is visible at a time, and a drop‑down menu enables you to select Volume, Pan, or one of the effects busses, to change the global values. At the bottom of the Track List is a draggable slider for overall Project Tempo and Project Key.

The third area is multi‑function, with various options selectable by clicking on the tabs at its bottom right. On first loading Acid it shows the Explorer (see page 176 again), which displays all valid WAV, AIFF or ACD files on every connected PC drive. The second tab is Properties (see above), and this opens up another window display which allows you to adjust track type, number of beats, root note, pitch‑shift and time‑stretch. Stretching allows markers to be positioned at the start of each beat in the file, so that it still sounds good when time compressed or expanded. Once you have tweaked and saved a file, it is referred to as 'ACIDised'. All ACIDised loops that have a root note specified will have their pitches shifted to match the Project Key mentioned above.

The third tab accesses the Mixer, where you can set the overall levels of any MME stereo output. Up to eight pre‑fade effects busses can be activated from Preferences. Each will have its own tab, and from here you can choose any DirectX plug‑in effect (see right), route each to any playback device, and control their overall level.

Grab A Wav

Most people will start by loading in some of the many demos provided on the CD‑ROM. But to discover the program's pièce de résistance, the Preview Loop function, click on any of the filenames displayed in the Explorer section. Within a few seconds, any selected file has been loaded and analysed for the number of beats contained within it, the original tempo, and the root note. This is clever enough, but the real‑time pitch‑shifting and tempo adjustment come into play immediately, and you hear the chosen sound or loop at the current project tempo and key. Not only that, but the loop can be previewed while playing your project. To put this simply, you set up a basic riff, and then point at any WAV file on your hard drive, and it immediately 'joins in', at the same tempo, and in the same key!

Once you have found a suitable loop (or single‑shot) sound, you can double‑click on it, or drag it directly into the Track View to create a new track. Any WAV or AIFF file that constitutes a track can have any number of events drawn in using a variety of tools.

The toolbar at the top of the Track View has the traditional Play, Pause, Stop, Go to Start, Go to End buttons that you would expect, along with Play Looped (you can set a mini‑loop of any length anywhere above the beat ruler) and Play All (to bypass the loop). The Record button allows you to create your own WAV files for use within Acid.

There are also six tools available from the toolbar.

• The Draw tool is used anywhere on the empty track to add events — as you continue to draw, more duplicated loops appear to fill the space, each showing the actual waveform.
• Select provides rubber‑banding for grabbing groups of events for moving elsewhere.
• Paint adds or erases events across multiple tracks, and is useful for quickly adding blocks of new sound.
• Erase deletes events with a left mouse‑click, but you can add them instead if you use the right mouse button.
• Zoom quickly changes magnification by drawing a box round the desired area.
• Envelope allows you to add volume, pan, and effects automation using lines overlaid on the waveform (see above). You can add a point, or drag an existing one, and link the points with a straight line (Linear Fade) or two curved ones (Fast Fade or Slow Fade). This automation method uses exactly the same techniques as the fade functions in Sonic Foundry's CD Architect.

Forging Ahead

Sonic Foundry are to be congratulated on a well‑written user interface. I found I had loaded up a bunch of WAV files and had written a song before I even glanced at the manual — it's that easy to use. The pitch‑ and tempo‑shifting do sound lumpy when taken to extremes, especially when transposing pitch up a long way (or tempo right down) from the original. However, the marker‑based stretching does ensure that the repeated sections are in time with the music, and this effect is obviously less noticeable with percussive material on which much loop‑based music is built. In fact, it is possible to treat it as an echo‑based effect, rather than seeing it as a defect.

If you run out of processor power, you can mix down multiple tracks to a new loop file, and even render the entire project into a single WAV file which you could then load into another editor, for final tweaks, or even a CD‑burning utility. Thankfully, Acid is not a closed system, since it can generate MIDI Time Code or MIDI Clock to drive another sequencer, or it can chase to incoming MIDI Time Code from another package (subject to the usual caveats when running multiple applications).

Coming Down

Acid probably owes its origins to the many tracker programs, but it does far more than these. Although it is still easy to produce predictable musical results, the easy addition of tempo and key changes (as well as the option to sync a MIDI sequencer), makes this far less likely.

If Acid had been released a few months earlier it would probably have wiped the field, but now it is not without competition. Programs like Mixman Studio (reviewed SOS February '98) provide all the fun elements of instant loop‑based music‑making at a bargain price of £40. Although this is currently a performance‑based environment with no editing, it still provides good real‑time pitch‑shifting. Acid is far more comprehensive than Mixman Studio, but at £249 it will not be a casual purchase.

Sonic Foundry's latest release is well thought out. It will appeal to anyone who works primarily with loop‑based music, and who wants some instant gratification. If this sounds like you, then don't let that money burn a hole in your pocket — let Acid do it for you instead.