[PD] metro and drift

[Damian Stewart]

hi,

After the comments on my previous post saying that metro drift wouldn't 
be too much of a problem, I ran a test or two, and roughly found this to 
be true.

I set up three metros, one to bang once every beat, one to bang every 
27th of a beat (triplet-based time), and one to bang every 49th of a 
beat (1/7th-based time). Then I left it running for a while, using timer 
and realtime to measure drift over each beat. The patch I used is attached.

Over 60 minutes:

Between whole beat and beat counted from 27ths:
realtime 0.002ms drift
timer 0.144ms drift

Between whole beat and beat counted from 49ths:
realtime 0.01ms drift
timer 0.149ms drift

Between whole beat counted from 27ths and from 49ths:
realtime 0.002ms drift
timer 0.007ms drift

Now, I'm not totally sure how to interpret these numbers, and certainly 
don't understand the huge discrepancies between realtime and timer 
outputs, but it seems like drift isn't going to be any problem for this 
amount of time.

As I understand it the human ear starts to hear things as two different 
events at around 15-20ms time separation, so in theory these drifts 
should be utterly inaudible.

The question is, will these .1 ms drifts be sensed even if not 
consciously audible? In the case of a hardware device like the Akai 
MPC2000, there's a whole mythology that's arisen around the 'perfection' 
of its swing function, being supposedly sub-ms accurate in a way that no 
other machine can match...

Hope this information is useful to someone :)

cheers
d
-- 
f r e y
live music with computers
http://www.frey.co.nz
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