Re: FlyLoops and electronic instruments

[Jeffrey Larson <jeff@zonemobius.com>]

 > but of course, would love to vary tempo and pitch separately.   
Have you
 > seen the REX2 standard by propellerhead ..... it's an audio format  
that
 > they claim allows flawless real time pitch/tempo shifting

REX2 is a file format for storing "beat sliced" loops.  It has nothing
to do with pitch shifting.  Beat sliced loops can be played back with
special software to achieve a form of time stretch, changing the tempo
without changing the pitch.  Basically loops are cut up into multiple
"slices", typically with a slice for each beat or fraction of a beat.
To change the tempo, the playback software shifts each slice closer
together (to speed up) or farther apart (to slow down).  This works
well for percussive loops with obvious beats and slices carefully
designed so they don't cut off sustained notes.  It doesn't work well
for non-percussive loops such as a legato horn line.

REX2 is just a file format, it doesn't actually do anything.  You
would have to write custom software to read the file and playback the
slices according to the desired tempo.  Creating new beat sliced loops
is usually not a real-time process.  You load a sample into some kind
of slice editor (like ReCycle).  Usually there is a way to have it
automatically determine slices based on amplitude spikes in the wave
form (the beats).  Then you can fine tune it manually by dragging the
slice markers or drawing new ones.  It can take some time to craft a
sliced loop that expands and contracts in a musically pleasing way.

REX2 is really only interesting for two things: 1) products that
want to play back pre-recorded loops from the vast sea of
sample disks and 2) loop designers that want to create content
for a loop file player that supports REX2.

Jeff