[LAU] Progressive Quantisation

Folderol folderol at ukfsn.org
Wed Aug 29 18:19:55 EDT 2007

On Tue, 21 Aug 2007 16:55:03 -0700
Bob van der Poel <bob at mellowood.ca> wrote:

> Nick Copeland wrote:
> > Hm, my reply to munging got damaged there!
> >  
> > Kurzweil developed a box to do this, I think as a project after selling 
> > his company to Young Chang. It was just such a PLL that would sync to 
> > the drummer so that the massively overproduced garange bands could play 
> > their music live, something that was impossible without  miming the 
> > whole act. Basically the drummer would lead the tempo (some are 
> > notoriously bad at following a set tempo anyway), from that the software 
> > would derive a MIDI time code and away it went to drive the sequencers.
> >  
> I remember, a long time ago, playing an Electrohome home organ which 
> varied the beat box tempo by following the timing the player used on the 
> pedalboard. I was young at the time (in the 60s) and I'm not sure how 
> well/badly it worked. But, I do remember the owner boasting about it :)

Sorry it's taken a while to get back to you, I've been on holiday.
I'm still trying to cope with the concept of a sunny August Bank
Holiday in Yorkshire! 

I did some work on PLLs at RF mmmfty mmmf years ago and seem to remember
that they are only really effective if there is a large difference
between the controlled signal and the rate of change, which I wouldn't
have thought would be true in this case.

This actually, isn't really what I'm after anyway. I want to do what is
potentially much simpler, I want to manage a completed MIDI recording
rather than working on-the-fly.

I would imagine something like:

Create a table of all the user-supplied reference notes.
Extrapolate further reference notes.
Calculate a best-fit curve.
Use curve to adjust all events (not just note on/off) on all channels
for even timing.

Sounds simple doesn't it :)
... bet it's not!

Will J Godfrey

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