Re: [linux-audio-user] Progressive Quantisation (long)

From: Larry Troxler <lt@email-addr-hidden>
Date: Sat Jun 17 2006 - 08:37:15 EEST

On Tuesday 13 June 2006 18:20, Mark Knecht wrote:
> On 6/13/06, Folderol <folderol@email-addr-hidden> wrote:
> > Well I don't know if this term actually exists or if I've just invented
> > it!
> >
> > This is an idea I've thought about for quite some time, years in fact,
> > but don't have the programming ability to try to put it into practice.
> > As I think it should really be part of, or a plugin to a sequencer I've
> > posted to LAU & Rosegarden lists. I hope nobody minds. I'd be very
> > interested in other people's thoughts on it.
> <SNIP>
> > What I would like to see is quantisation algorythm the detects trends
> > rather than absolute values, then progressively applies small
> > corrections the keep overall timing correct. (it would of course have
> > to operate over all tracks simultaneously).

So you have this tempo-imprecise piece of playing that you've recorded, and
now you want to quantize it in such a way that the resulting performance
follows a strict metronome throughout the whole piece?

If so, then might I offer a thought here? it seems to me that what you are
asking for is a beat detector, followed by tempo editing.

I think that this would be a more general purpose feature set that would still
accomplish what you want to do. Consider that often (at least in my case) I
would like to detect the beats, but _not_ to correct the tempo, since to me
at least, the slight variation in tempo sounds natural and captures the
original spirit of the recording. However, I might like to add additional
tracks that are synchronized to this meandering tempo, and also would like a
notation display of the tempo-meandering performance.

So in my case, I would run the beat detector, which would generate a tempo map
and adjust the event times> The end result would sound the same as the
original performance. In your case, you would take the additional step of
then editing the tempo map to clear out all the generated tempo changes. That
is, if I understand what you want to do correctly.

Of course, there's always the possibility to provide an option in the
sequencer's beat detector dialog, to not change the tempo map, and only
adjust the event times.

There is some prior art in studying beat detection algorithms - consider

> Anyway, the thought I was having had to do with the need to discover
> which hits were intended to be on the beat, whatever that is, and
> which hits where these ghost notes. IMHO a good tool for changing MIDI
> tempo would determine which is which and would vary the tempo without
> making huge changes to the time between the main hit and it's ghost.

Would this in practice be an issue if the tempo doesn't vary wildly? If it is
an issue, I guest there are several possible approaches to deal with it. And
exercise for the reader, as they say? :-)


Received on Sat Jun 17 08:15:01 2006

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