Hmmm... I am not sure where Avery Burdette got this information about 32nd
note offsets! Neither, can I confirm whether he is correct concerning the
CS6x, S80, S30 etc (since I don't own any of these machines).
However what I can say is that this is definitely NOT the case with respect
to AN1x or PLG150AN. Both of these devices provide the arp/seq in a standard
way....and both synchronise correctly to MIDI clock. From my experience,
where problems arise over synchronising devices, they can always be traced
back to the quality of the source MIDI clock!
Basically MIDI clock is transmitted as an F8 MIDI real time message at a
rate of 24 per quarter note (so for example the time between clocks at
100bpm is 25ms). The hardware device uses a phase locked loop (PLL) to
synchronise to these messages and thus stay in tempo with other devices.
However it should be noted that MIDI is a serial transmission protocol,
where most messages take around 1ms to transmit. This means that you cannot
have multiple MIDI events occurring at the same time i.e. they must be
queued serially. Consequently, during the average multi track MIDI sequence,
you will find there is a variable latency (from when events are scheduled to
play...to when they actually play) of around 1ms to 10ms. (If you have a
large volume of sysex or controller data, you can find these latencies
getting quite high....and thus causing quite noticeable instabilities in the
timing).
Obviously such latencies will introduce a high degree of variability into
the MIDI clock timing (i.e. the period could vary widely. In the case of the
example above of 100bpm, a variable latency of 10ms would give a timing
variation of +/-40% or an apparent tempo variation of 71bpm - 166bpm).
However, PLLs average over several periods, so small variations are evened
out. However if the clock is erratic, the PLL will find it difficult to
capture and track....thus the apparent tempo of the slaved device will jump
sporadically. Such faults will be manifest as the playback device stuttering
or dropping notes etc.
Fortunately, the MIDI specification attempts to overcomes this problem by
stating that MIDI clock must be given priority over all other queued MIDI
events (i.e. MIDI clock events go to the top of the queue). If this is
adhered to then the clock is always transmitted at the correct time and the
period should only vary by around 1ms.
Unfortunately, several [well known] software sequencers do not appear to
follow the MIDI specs....or alternatively give timing performance preference
to audio functions .....the result being that their MIDI clocks are
unstable......and thus syncing hardware equipment can be problematic!
Hence if you are having problems, my advice is to use a MIDI monitor (either
hardware or software e.g. MIDIOX) to inspect the sequencers MIDI clock
output, before blaming the hardware!
Of course the best solution when slaving multiple devices and software is to
use a hardware clock source. That way you are sure of a good source. If you
try this with either An1x or PLG150AN, you should find they synchronise in a
rock solid manner!
Regards
Gary
Email:
gary@...http://www.yme.co.uk/yme > -----Original Message-----
> From: lars.l.arnwald@... [mailto:lars.l.arnwald@...]
> Sent: 08 May 2000 09:44
> To: AN1x-list@egroups.com
> Subject: [AN1x-list] Yamaha Comments on Seq/Arp timing
>
>
> Hi Jon!
>
> I haven't been able to follow the earlier comments about the
> synchronization delay problem you're mentioning, but since I'm on the
> verge of adding a PLG150-AN card to my MU1000R I have to ask you
> about
> some points out of the answer given by the Yamaha product manager Mr.
> Burdette. I suppose he should answer my questions, but I start with
> trying to get your opinion.
>
> "....the triggering implementation (both internal and through MIDI)
> is
> a little different from previous instruments. But it does synchronize
> perfectly with external MIDI clock messages recieved by the MIDI in
> of
> the CS6x®, S80 and S30...."
>
> I really don't know which previous instruments he refers to. What is
> different here?
>
> "....The reason that it doesn't seem to sync properly is that the
> actual arpeggio pattern is offset (delayed) by a 32nd note
> (independant of tempo as it must be, to be in sync). This is a
> predictable musical value that represents a "window" of
> opportunity
> that the arpeggiator gives you in order to determine how many and
> which notes you wish to arpeggiate...."
>
> I intend to slave the arpeggiator to an external tap tempo function.
> Will I always be a 32nd note late? The last sentence seems a bit
> cryptic. What do you get out of it?
>
> "....When you are aware of this 32nd note offset, it is possible to
> trigger manually (by anticipation of a 32nd note) to achieve the
> desired result, and through MIDI by offsetting the arp trigger
> note[s]
> by a 32nd note...."
>
> I guess I could learn to tap a 32nd early, but if precise results are
> required this may not be possible. What if I slave some other unit to
> the tempo tap, will there always be a glitch between them?
>
> Just a few ago I tried a PLG150-AN sitting in a CS1x. Even though I
> could only use earphones I could definitely hear the might of the
> sounds and I really liked the arpeggiator. My two trusty Cyclones
> I've
> had for over ten years are great but hard to program. This one seems
> so much easier and all the patterns I tried sounded musical. OK I
> shouldn't panic, but these news dishearten me a bit.
>
> Best regards,
> Lars
> lars.l.arnwald@...