How do you change rate without altering pitch?

[Jeff]

If you're not already a member, you may want to search the archives on the Loopers Delight mailing list. The "looping with a drummer" topic has come up several times. Unfortunately since not many people there use a Repeater any more, the solutions usually end up with the looper being in control of the tempo and figuring out ways for the other performers to follow that, usually by making the loop audible to everyone with some form of monitor. I think someone even rigged a light that would pulse the tempo and be visible to the drummer, then everyone follows the drummer.

Drummers of course HATE this, but there aren't a lot of good alternatives.

If the tempo stays mostly the same but just drifted a little another common technique is to use Retrigger to restart the loop from the beginning. When you start hearing the loop dealign with the drummer wait for the downbeat of the first "measure" and Retrigger to bring the loop back into alignment. But if you want to adapt to ritardondo or accellerando then you're out of luck.

I'm currently doing a lot of work on rate/pitch shift so I'll revisit this and see if there isn't some way we can get close to time stretch.

[serr]

Originally Posted by Jeff

the solutions usually end up with the looper being in control of the tempo and figuring out ways for the other performers to follow that, usually by making the loop audible to everyone with some form of monitor. I think someone even rigged a light that would pulse the tempo and be visible to the drummer, then everyone follows the drummer.

Drummers of course HATE this, but there aren't a lot of good alternatives.

Yeah... That's simply not music to me! Too mechanical.

Originally Posted by Jeff

If the tempo stays mostly the same but just drifted a little another common technique is to use Retrigger to restart the loop from the beginning. When you start hearing the loop dealign with the drummer wait for the downbeat of the first "measure" and Retrigger to bring the loop back into alignment.

Yep. I do that.

Originally Posted by Jeff

I'm currently doing a lot of work on rate/pitch shift so I'll revisit this and see if there isn't some way we can get close to time stretch.

Very cool! Thanks Jeff.

[Jeff]

Well I'm happy to report that I was able to get a rudimentary version of time stretch working last night. It builds on my recent changes to allow speed and time to be changed continuously rather than quantized to semitone steps. This will be called "Speed Bend" and "Pitch Bend". I added a "Time Stretch" control that basically just sets a speed bend with the inverse pitch bend and it worked surprisingly well.

Once you get beyond the equivalent of a few semitones it does start to have some obvious audio artifacts though. Not completely useless but not exactly pleasant for some styles of music. I've still got some issues to work out, pitch shift has always caused an brief gap of silence because we're adding another level of buffer which has to fill and adds latency. You don't notice this so much with semitone steps but when sweeping with a CC or pitch bend wheel it doesn't sound smooth. But I'll try to get it cleaned up and release something in the next week or so.

[serr]

Originally Posted by Jeff

Well I'm happy to report that I was able to get a rudimentary version of time stretch working last night. It builds on my recent changes to allow speed and time to be changed continuously rather than quantized to semitone steps. This will be called "Speed Bend" and "Pitch Bend". I added a "Time Stretch" control that basically just sets a speed bend with the inverse pitch bend and it worked surprisingly well.

Once you get beyond the equivalent of a few semitones it does start to have some obvious audio artifacts though. Not completely useless but not exactly pleasant for some styles of music. I've still got some issues to work out, pitch shift has always caused an brief gap of silence because we're adding another level of buffer which has to fill and adds latency. You don't notice this so much with semitone steps but when sweeping with a CC or pitch bend wheel it doesn't sound smooth. But I'll try to get it cleaned up and release something in the next week or so.

You rock!

[PalmWino]

Mmmmmmmm!! audio artifacts!
Dave

[unguitar]

hey Jeff,
this thread is becoming very hot and I like this sentence of yours a lot: "I was able to get a rudimentary version of time stretch working last night".

This is great news !

thank you for working on this,
Luca

[unguitar]

ah !
just in time to say this thread was becoming superinteresting and everybody disappeared...

hello ?
where did you move the party to ?

[Jengel]

+1

I can't wait to hear the timestretching, hopefully it will be in the august release

[Jeff]

In case anyone is subscribed to this thread, release 2.2 of Mobius adds a form of time stretch using the new appropriately named control Time Stretch. I still consider this a work in progress though since it uses the old pitch shifting algorithm and as such introduces a lot of additional latency. But it can be fun to play with in some situations.