LOGIC NOTES

Tempo Operations

Published in SOS October 2002
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Technique : Sequencing & MIDI Controllers

More advice on writing music to picture, and some useful pointers for users of EXS24. Plus another fine crop of tips from the pros.

Empty objects within a blank track in the Arrange Window can be locked against SMPTE time to act as hit point markers.

In SOS August 2002 I provided an introduction to using Logic as a tool for producing music for picture, and looked at some of the synchronisation issues when working either from external video playback or digitised video clips. The next thing to consider is how Logic can help with two further technical issues: marking the position of 'hit points' within the musical sequence and calculating tempos needed to get from one hit point to the next exactly on the beat.

Hit points are events within the video footage that need to be reflected in some way by the music, such as dramatic events in the on-screen action, cuts from one camera angle to another or transitions from one scene to another. Here's a simple example to illustrate the idea — a set of SMPTE hit points for a Film Short called Boy Meets Girl (a love story):
01:00:00:00: Boy smiles nervously at girl.
01:00:04:00: Cut to girl smiling warmly at boy.
01:00:07:08: Cut to overhead shot as boy and girl embrace.
01:00:08:07: Cut to boy and girl walking into sunset together.

In this sequence, there is a period of four seconds between the start of the action and the next hit point. In four/four time at 120bpm, this represents exactly two bars of music. However, a problem arises if, having composed a suitable two-bar tune, the tempo feels wrong (perhaps it does not reflect the tentative uncertainly of teenage male love suggested by the visuals!). Unfortunately, simply entering a slower tempo into the Transport window is not a solution. For example, if the tempo is changed to 90bpm, the four-second, two-bar melody becomes a more relaxed 5.3-second, two-bar melody — but the video footage still cuts to the girl smiling after four seconds. Two observations arise from this simple example. First, the visual hit points are fixed in (SMPTE) time; and, second, the issue of tempo can be much more complex in composing music for picture than for the majority of music-only projects.

It is useful to have a visual indication of where hit points occur within a sequence, and Logic's Markers can be used for this. The Song Position Line (SPL) can be positioned at the required SMPTE time by clicking on the SMPTE time position within the Transport window. Once this has been done, a Marker can be created at the SPL via the Marker submenu of the main Options menu. If you select Open List from the same submenu, each Marker can be locked in SMPTE time from the SMPTE Position submenu of the Marker List window's Options menu. However, one disadvantage of Logic's Markers is that the Marker List displays positions in bar/beat time rather than SMPTE time, and this can make the process of repositioning Markers a little tricky.

A simple and useful alternative uses Logic's Event List. This list can display object positions in SMPTE time — open the Event List window and then select Position & Length In SMPTE Units from its View Menu. Visual hit point cues can be created using an empty sequence object (or series of sequence objects) on an unused track within the Arrange Window. One of these can be positioned at the exact SMPTE time of each hit point and then locked to that SMPTE time position (from the Functions menu's Object submenu), and it helps if you also switch on the SMPTE time ruler from the View menu. Even if the tempo of the song is changed, these sequence objects will stay fixed to their original absolute time position, but if they do need to be repositioned, this can easily be done in SMPTE time units via the Event List.

As indicated above, when writing music for picture there are often going to be hit points that do not fall exactly on the start of a bar or beat. There are a range of creative solutions to this problem, but one approach is to insert tempo changes within the sequence. However, working out the required tempo changes by hand (or even with a spreadsheet) is a rather laborious process. Fortunately, Logic's various tempo manipulation functions can help here.

For example, the Tempo Operations Window (accessed from the main Options menu's Tempo submenu) can be used to calculate either a fixed tempo or a tempo curve that produces an exact number of bars or beats between two SMPTE time locations. Once the start and end SMPTE times are entered, these should be locked (click the padlock to close it). If the tempo value is then adjusted (click and drag on the value with the mouse), the end position in bars/beats will change automatically — simply change the tempo until the SMPTE end time falls conveniently onto a beat. In this example, a tempo of 72.29bpm gives exactly one bar of music between the second and third hit points. Activating the Continue With New Tempo option causes this new tempo to be retained beyond the end SMPTE position.

Sometimes a gradual tempo change provides a smoother way to move between hit points. Screenshot 3 shows an example of this using the same two hit points as above. First the Create Tempo Curve needs to be selected from the drop-down list. Once the start and end SMPTE times have been entered and locked, the Curve Type, Curvature and Density (the frequency of individual tempo changes used to produce the overall curve) can be set. The end tempo is then adjusted with the mouse until a suitable combination of tempo and bar/beat values is found.

There are alternative approaches to dealing with hit points and bar/beat structures. These include inserting the occasional bar in a different time signature or just ignoring the sequencer's tempo altogether and just playing along 'free form' with the visual images (as a live organist played along in the pre-sound days of cinema). Of course, the latter also makes it rather difficult to use both quantise and score functions, so experimenting with some subtle tempo changes is often a good starting point.

Logic Tips     When you want separate sequence objects for each drum in a complex drum sequence, select the object in the Arrange window and choose Demix By Note Pitch from the Split/Demix submenu of the Arrange Window's Functions menu. Len Sasso You can often 'humanise' a MIDI sequence by applying slight random variations to note positions, velocities, or lengths. With the Transform window, it's a piece of cake to do this — just select the notes to be modified using either Transform conditions or by selecting them in one of the MIDI editing windows, then use the '+-Rand' operation from the drop-down menu below the desired MIDI parameter. Len Sasso If you want to move your Sampler Instruments folder to another location — say the external drive where you store your samples — remember to place an alias/shortcut in place of the original, named identically, so that Logic can still find the files it needs. Paul White Although the Environment's Touch Tracks object is designed only to play MIDI sequences, you can trick it into playing audio as well if you have a sampler instrument plug-in — drum samplers work well for this. Just load the audio clips you want Touch Tracks to play into the sampler and create MIDI sequences to trigger those samples in any order and combination you choose. Then drag those MIDI sequences into the Touch Tracks window and use Touch Tracks to trigger them. Bear in mind, though, that you will need Use Unified Virtual And Classic MIDI Engine turned on in Logic's Preferences for this to work. Len Sasso Most Logic windows have various cursor tools available. You can assign Key Commands to select individual tools or to step incrementally through the window's toolbox. Also the Command key (Control key on the PC) will toggle from the current tool to an alternate tool of your choice. Assigning an alternate tool is the fastest way to switch between selecting and naming sequences in the Arrange window or between cutting and pasting notes in the Matrix Edit window, for example. Len Sasso

Combining Split Sample Programs In EXS24     Many sample library CD-ROMs were designed back in the days when samplers had 32MB memory limits, so you'll often find large string or piano sample sets split into two-octave sections or similar. You can combine these into single EXS24 sampler Instruments very easily simply by opening the Instrument Editor, using the Select All keyboard command followed by the Copy command. If you then close this window and open up the Instrument Editor for a new EXS24 Instrument, you can execute a Paste command and all the copied samples and Zones will be added. Repeat this process until you've added all the necessary elements from the individual sample programs, then save the result with a new name. Paul White

Logic v5.2 Enhances Audio Engine & EXS24     Emagic have released Logic Platinum v5.2, an extensive update containing many features that users have been requesting for some time, including support for VST Instruments with multiple outputs via a new submenu. All outputs are automatically summed to the output of that Instrument channel, until you assign the other outputs from the new aux Audio objects, which are then intelligently subtracted from the master output. Of Logic's own instruments, when selected from the multi-channel instrument menu, EXS24 now supports five stereo and six mono outputs, which are also handled via the new aux channels. This allows different groups or zones to be routed to different outputs, which will be great for drum patches. And EXS24 can now import Giga libraries, which makes installing the Virtual Memory extension a must for handling large file sizes. The audio engine has been enhanced and now supports up to 128 stereo tracks on a single audio card (previously 96), 256 stereo tracks across multiple audio hardware (previously 192), 15 inserts for each track and buss (previously eight), 64 busses (previously 16), 64 instruments (previously 32), and 64 aux channels, supporting a maximum of 64 multiple outputs from all instruments running. A new instrument has been included, the rather curious rough-and-ready KlopfGeist, a simple percussive synth perfect for bass drums and the lead line in covers of Jean-Michel Jarre's 'Popcorn'. However, the real point of KlopfGeist is to be used as a simple and effective internal metronome sound, which can be easily routed around the Logic mixer. Logic will automatically assign the 64th audio instrument object to KlopfGeist when required and, theoretically, any other instrument assigned to this object could take the place of KlopfGeist for metronome playback. Logic's ability to handle effects while recording has been improved and finally allows you to monitor a regular audio track with effects when that channel is record-enabled. You can also record with insert effects by assigning an Input object to the input of an audio track. And a useful real-time sample-rate conversion feature has been added, so a song recorded at 96kHz, for example, can be played back correctly on another computer that can only handle a maximum sampling rate of 48kHz. The list of new features goes on, and we'll be looking at these in more detail in forthcoming columns. This is a must-have update, and both Mac and Windows users can freely download it from www.emagic.de — you even get a free four-week trial of Emagic's new EVD6 virtual clavinet instrument. Mark Wherry