Audio Compositor 4.1 Release Notes

Welcome to Audio Compositor 4.1!  If you upgraded from version 4.0,
this release brings you some minor sonic improvements:

•	Output from the realtime synth is a bit cleaner.

•	The renderer adds dither noise when creating 16-bit output .wav files.  If you don't know what this means, don't worry about it!

If you're upgrading from an even earlier version, you'll find a lot that's new here.  The instrument editor has been redesigned to make more flexible use of screen space, and to speed large copy/paste operations.  The MIDI renderer is faster, and instrument amplitudes are now dead accurate.  There's also DLS level 2 support, and other new features: for more detail read on.

Revised instrument editor

The instrument editor has changed significantly.  The left-hand tree view, and the property sheets for articulation parameters are still there, but the upper-right quadrant of the screen is now occupied by up to three different windows, which may be turned on or off in any combination.  The idea was to take advantage of large display devices (i.e. resolutions over 800 x 600) while keeping the program usable on smaller screens.  The three views are:

•	The region grid, used to map samples to the keyboard; this is not greatly changed from previous versions.  A new button in the lower-right hand corner switches the grid to “edge-locked” mode, meaning that when you move the border of a region its neighbor automatically moves along with it.
•	The list view, which displays the children of the object currently selected in the tree view.  This is meant to mimic the Windows Explorer, and to simplify drag-and-drop operations.  In particular, it’s now possible to select more than one item in the list view (by clicking with the SHIFT or CTRL keys) and drag them into the tree view or into another editor window.  In previous versions of Audio Compositor, you could only drag one item at a time.
•	The wave view, which graphs the current sample (when the selected object is a sample).  If you don’t have a large monitor you’ll normally want to turn this window off.

The three views are enabled or disabled using the buttons to the right of the articulation tabs; the magnifying-glass buttons give you some control over their relative sizes.

“Adjust SoundFont attenuation” for correct instrument balance

A new checkbox in the preferences tells Audio Compositor to interpret the SoundFont initial attenuation generator the way most sound cards do.  Previous versions of AC interpreted the value literally, which could incorrect relative levels between instruments when rendering with SoundFonts.  We recommend checking this box unless you specifically require Audio Compositor’s old behavior.

External wave editors

Audio Compositor has a rather feeble built-in wave editor, which we’ve retained through the years mainly because of the ease of integrating it with the rest of the program.  It also has one feature rarely seen in wave editors: it understands fractional loop points.  As far as we know, if you want to create loops with sub-sample precision (and Audio Compositor’s playback engine does know how to render such loops), you’ll need the Audio Compositor wave editor.

Nevertheless, most Audio Compositor users will have a dedicated audio editor on hand, and will prefer to use it for most sample-editing chores.  Audio Compositor can now use an external or “alternate” editor if you specify its location in the Preferences window.  Doing so activates an extra menu item in the instrument editor: for example, if you right-click on a sample, just below the old “Wave editor” option you’ll find a second option called “Wave editor (coolpro.exe)” or something similar.  Editing a sample causes its wave to be extracted to a temporary file called “AC Temp 000000.wav” (the numeric part will increment as you edit subsequent files).  When you save an instrument bank, the instrument editor retrieves the contents of any outstanding temp files and commits them to the instrument bank.  If you modify a sample in a wave editor, and want the modified sample saved to a DLS or SoundFont file, you must save your work from the wave editor first, and then save the instrument bank.

DLS Level 2 support

Audio Compositor will now read and perform DLS Level 1 or Level 2 files, and can write DLS files that can be read by both Level 1 and Level 2 devices.  Because the Level 2 specification is more comprehensive, less information is now lost when an instrument file is saved in DLS level 2 format.

Several changes to the instrument editor are designed to make Audio Compositor a friendlier environment for DLS and SoundFont files.  Envelope generators are a good example.  Traditionally in Audio Compositor, envelopes can have any number of segments and can be drawn with the mouse in virtually any shape.  While this flexibility has some advantages, it’s at odds with the rigidly-defined six-stage envelopes which are becoming standard in other applications.  Audio Compositor envelopes now come in two varieties.  A “six-stage” envelope has the standard segments (delay, attack, hold, decay, sustain, release) and can be written to a DLS or SoundFont file without modification.  The older type of free-form envelope is now referred to as a “custom” envelope.  Avoid custom envelopes unless you will be saving your work to Audio Compositor’s native .ACP file format; they’ll be simplified as necessary if you write them to a DLS or SF2 file.

Modulation routings are a similar story.  In earlier versions of Audio Compositor, you could use the mouse to draw an arbitrary relationship between a modulation source (e.g. the mod wheel) and a destination (e.g. an LFO depth).  That relationship is referred to as a “transform” in today’s jargon.  The traditional freehand routing is still available in Audio Compositor, but you must ask for it by selecting a “custom transform”.  By default, Audio Compositor will create modulation routings with a standard linear transform, in which the modulation source is applied to the destination using a simple straight-line relationship.  (An exception to this rule is that MIDI velocity, volume, and similar sources are routed to output volume using the inverse concave transform found in most synthesizers.)  These pre-defined transforms are the natural mode of expression in DLS and SoundFont files.  “Custom” transforms, like custom envelopes, must undergo a somewhat unpredictable simplification process if they are saved to something other than a native .ACP file.

In addition to the linear and inverse-concave transforms just mentioned, a variety of standardized transforms are also available.  You can select these on the instrument editor’s “Key Routings” and “CC Routings” tabs, but most of these can only be saved to Audio Compositor’s .ACP file format.  Modulation routings cannot be saved to SoundFont files because Audio Compositor does not currently support the SoundFont 2.1 specification.  The range of modulation routings that can be saved to a DLS Level 2 file is limited by the DLS specification to the following:

Key routings:

•	Velocity to envelope attack time (linear transform)
•	Key number to envelope decay time (linear transform)
•	Key number to envelope hold time (linear transform)
•	Velocity to filter cutoff (linear transform)
•	Key number to filter cutoff (linear transform)
•	Velocity to volume (inverse concave transform)

Continuous routings:

•	Controller 1 to LFO1 amplitude, pitch, or filter cutoff (linear transform)
•	Aftertouch to LFO1 amplitude, pitch, or filter cutoff (linear transform)
•	Controller 1 to LFO2 pitch (linear transform)
•	Aftertouch to LFO2 pitch (linear transform)
•	Controller 7 to amplitude (inverse concave transform)
•	Controller 11 to amplitude (inverse concave transform)

Reverb and Chorus

Audio Compositor 4.0 supports reverb and chorus effects.  The chorus effect is fairly conventional: delay and detune values can be specified in the Preferences.  The polyphony requirement is doubled for instruments using this effect.

The reverb effect is intended for casual use.  Users who know chalk from cheese will continue to do what they’re doing now: for example, adding reverb in post-processing with a proper audio editor. 

Limited-polyphony rendering

The MIDI file renderer can now be told to limit its polyphony (the setting is at the upper right edge of the renderer window).  This apparently backward feature is useful when you have a combination of an instrument with unusually long release times, and a MIDI file that triggers a large number of notes in this instrument, on the assumption that the resultant buildup of voices will be limited by hardware.

Frankly, it’s also a marketing ploy.  In unlimited-polyphony mode, AC performs much more slowly than software synths that do traditional voice stealing.  Displaying the polyphony setting at the top of the window makes it a bit clearer what is going on.

Miscellaneous

Every release of Audio Compositor includes countless small refinements suggested by users.  We receive hundreds of these each year, and if you’ve written to us recently, the odds are about 50/50 that your suggestion made it into Audio Compositor 4.0.  If you don’t see it in this version, feel free to nag us again.  See you next time!