Originally Posted by dcuny
In short, a RealTrack performance is an audio file where someone is playing an instrument over many chord changes of various lengths (bar, half bar, beat level). However, you never deal directly with RealTracks like this.

Instead, you specify a chord sequence in BiaB interface - basically, like in a spreadsheet. BiaB automatically pulls the chords out of the selected RealTrack to match the order you specify.

The algorithm works at the bar/half bar/beat level, not by working on the material at the note level. It can force the notes to match the chords via pitch shifting, but that's not generally what happens.

Think of it sort of alike automatic loop assembly. Obviously, there are a finite number of chords in any given RealTrack, but they're generally long and diverse enough that it isn't a problem.

As to how well it works, you can check out the demos here: https://www.pgmusic.com/tutorial_realtrackslist.htm
Excellent explanation David. A couple things I'll add:

RealTracks are more than single audio files - they're multiple performances (between 5 and 70 separate performances) done in multiple keys. Some RealTracks rely on at least some pitch shifting (2 semitones max) while others are recorded in all 12 keys. The amount of audio content for each RealTrack is anywhere from a couple minutes for the simplest ones (Jaw harp) up to over 3.5 hours for the most complex (Vocal oohs and aahs).

Drums are similar, however there are a couple differences. Since drums aren't required to match the chord of the song there isn't any pitch-shifting going on. However, there are often different variations of drum grooves - for example, open hi-hat vs closed hi-hat vs ride cymbal, or snare vs side stick.

This is the full list of chords BIAB supports. We try to record as many as possible, however on some instruments there are many chords that are overly difficult or impossible to play, so in those cases BIAB will substitute something close.

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