> Dan Wilson wrote:
>
> I'm fairly ignorant of MIDI, but I understand that the signal for a
> note start arrives at the same time as the signal for its velocity,
> the latter having been measured over the previous 1/3 second or so as
> the key descends.
>
> Obviously an electronic instrument can immediately start an
> appropriately soft or loud note, but how can you synchronise an actual
> solenoid-operated acoustic piano to what is happening somewhere else
> live, when to do the replication it must know what keys are starting
> to be pressed, not just when audible notes occur ?
>
> With MIDI, am I right, it can only start moving the key when the
> originating piano has finished moving its own ?

I don't boast myself as a computer guru by any means but best to my
knowledge the process is this:

Before any note can play the information on "how" to play the note must
arrive first.  (It doesn't do any good to send the command to play a
note and then send the velocity data after it has already played).
This of course occurs in a hundredth of a second and is unnoticeable
in human terms.

PianoDisc uses a format called MIDI Type 0.  This means that the data
is fed into the processor in a continuous stream as opposed to being
stored in a cache.  The other type of MIDI, called MIDI Type 1, is what
most of use are familiar with on our computers, where the data is first
loaded via a file and then played.  In either format the actual command
structure is the same.  One can be easily converted to the other with
some simple software.

 [ Type 0 and Type 1 are different types of _disc file_ formats, as
 [ contrasted to the signals on the MIDI wireline.  Type 0 format
 [ stores all the events ordered by time, which is most convenient for
 [ external synthesizers and pianos.  Type 1 format is ordered into
 [ 'tracks' especially for use by editing programs.  -- Robbie

As far as "real time" is concerned, transmitting data of this sort
over the Internet would actually be best described as "relative time".
A slight delay is unavoidable.  The same could be said for "live"
television broadcasts.  From a live camera shot the signal must go
through a remote processor, enter a microwave transmitter, be received
by the studio, be processed again, rebroadcast via the air or on cable,
and then to the viewers home.  By the time the audience sees it there
is a 3-4 second delay.

Likewise would have to be said for a "live" MIDI broadcast on the
Internet.  While a pianist may be playing a piano live, the signal
would be reaching your PianoDisc a few seconds later.  Again, in human
terms it is irrelevant.  As far as the listener is concerned, it is in
real time.

From what I understand these are the basics.  If anyone more MIDI
knowledgeable can add to this, please do.

Rob Goodale