Re: AU2 - beatAndTempoProc
Re: AU2 - beatAndTempoProc
- Subject: Re: AU2 - beatAndTempoProc
- From: "James Chandler Jr." <email@hidden>
- Date: Tue, 24 Sep 2002 12:09:06 -0400
>
Surely using the denominator is the least guess work seeing as the
>
"beat" is 99% of the time divisible by this number, no?
>
As has been mentioned, often 6/8 is compound so a quarter note would be
>
simply incorrect...
Hi Lachlan
Marc Poirier's original message in the thread was solid and
well-considered...
http://lists.apple.com/mhonarc/coreaudio-api/msg02339.html
Marc mentioned that "beat" should be unambiguously defined, and he listed
additional info items which would be very useful to a plugin.
In many modern sequencers, there are at least two "beats" which are
important for good flexibility.
1. The tempo beat, as in "quarter note = 120 BPM" or "dotted eighth = 120
BPM" or whatever.
2. The metronome click beat, which can be entirely different, whatever is
most convenient to help the composer get the correct metronome "feel" in a
piece. In 6/8, the metronome click beat would typically be a dotted quarter,
though some other value might make sense in context of a particular
composition.
A tempo-change event would use the tempo beat as a reference, and a
time-sig-change event would use the metronome click beat as a reference.
In many cases, it is entirely reasonable to use quarter note as the tempo
reference beat for an entire song, but to change the metronome click beat
along with each timesig change. But armed with both variables, the composer
is free to arbitrarily change the tempo beat and the metronome click beat
anywhere it is convenient.
As Marc said, it would be very useful if sequencers and plugins can
communicate both items of information. Info items should be well-documented
as to intended function, so that a plugin would give predictable results in
different host programs.
Marc's list mentioned other desirable stuff, including a Bar-start info
item.
James Chandler Jr.
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