[Fluxus] Fluxa midi sync

[Kassen]

Dear list,

For reference; I just pushed midi sync for fluxa into Redacted.

Usage;

Plug in a midi cable with a clock on it and (midiin-open ) the
relevant port. If a midi clock message is heard there (seq ) will
automatically sync to it (ignoring proc's return value).
(midi-set-signature ) will set how the clock is interpreted. Notes
will be scheduled one bar's duration into the future with a "clock"
value that corresponds to the number of beats according to the current
time signature since the last clock start message. In practice that
should mean it should "just work".

I also changed (set-midi-signature ) a bit in that it no longer resets
the clock position but instead attempts to come up with a sensible new
value. Changing from 4/4 to 8/8 should keep you in exact sync, for
example. The old behaviour reset the song position to be 0 at the
moment the function was invoked, which often didn't make a lot of sense.

(set-global-offset ) can be used to compensate for any soundcard
latency, that function was already there for "slub sync" so I thought
I'd use it too.

On the downside; a lot of modulation of the clock that we slave to
will cause a mess in the sound. Not in the actual tracking, but we
have to schedule ahead based on the exepcted duration of beats that
are yet to come so that's unavoidable.

I hope this is useful to somebody. Without wanting to critique the
various methods of syncing laptops to laptops in advanced ways; there
are moments when it's quite nice to be able to sync to a oldfashioned
drummachine in a very simple way.

Yours,
Kas.