Disklavier

> On Oct 8, 2007, at 1:00 PM, Kevin Goroway wrote:
> 
> > I'm under the impression that the playback of MIDI from the CD is  
> > still done via an analog connection, and the capabilities of that  
> > are lower than when playing them directly off of floppies.

On Tue, 9 Oct 2007, George F. Litterst wrote:

> The purpose of creating PianoSoft Plus Audio CDs was to provide a  
> simple medium for combining the MIDI data that drives the piano with  
> real audio (singers and/or instrumentalists). The solution was to put  
> the singers and instrumentalists on one audio channel of the CD and  
> to encode the MIDI data as audio and place it on the other channel.
> 
> That scheme worked very effectively, and I don't believe that  
> Yamaha's solution has compromised the MIDI data. In other words, the  
> Disklavier plays the MIDI data in the same way that it would play  
> MIDI data that is received over a MIDI cable.


I believe Kevin's understanding is correct - playing MIDI data from a
Yamaha CD is slightly inferior to playing it over a MIDI cable, and
*definitely* inferior to playing a MIDI/ESEQ file directly from a floppy
disk, memory disk or hard drive.  This goes for all Disklavier models.

The reason?  MIDI data on CD is encoded with extremely limited bandwidth
(12.6 Kbps, as compared with a 31.25 Kbps wireline MIDI connection,
which itself is considered quite slow by today's standards).

MIDI events on a CD take longer to send, due to the limited bandwidth,
and large chords may become slightly more arpeggiated.  The time between
events is encoded as simply idle time on the CD; there is no concrete 
indication of precisely when a MIDI event should fire.

In contrast, MIDI or ESEQ files played from floppy disks or the
Disklavier's memory can be played with more accurate timing, since MIDI
and ESEQ files precisely specify when each event should fire.  A
Disklavier can strike all notes of a ten-note chord simultaneously when
playing from a floppy.  When playing from a CD, it would take about 19
milliseconds to transmit all of the MIDI events for that ten-note chord,
so the chord would inevitably play with a slightly arpeggiated effect
(which, depending on the listener, may or may not be noticeable, though
studies have shown that trained musicians can discern timing variations
of under 5 ms).

Time to transmit a ten-note chord
=================================
Floppy:     0 ms
MIDI cable: 7 ms  (best case; if running status is used)
CD:         19 ms

Zenph Studios has mentioned that they perform all of their recreated 
performances from the internal disk drives of the Disklavier.  This is 
to avoid the timing inaccuracies introduced by wireline MIDI and by the 
"analog MIDI" CD format.

With that said, the CD format Yamaha uses is much better than the
formats of PianoDisc and QRS, which are both over 3x slower!

But QRS is introducing a new piano+audio CD format called "SPA-Logic"  
which is designed to improve the timing a bit.  It also offers some
interesting technical features: you can play these discs on your home
stereo as normal audio CDs (and hear the piano part etc.)  But when
played on the player piano, the piano is able to completely remove the
acoustic piano audio from the mix (due to special encoding tricks
applied to the sample data when the CD was mastered) and play from MIDI
events embedded in the subcode.  These SPA-Logic CDs also permit
on-the-fly enabling and disabling of other elements of the mix (vocals
etc.) according to the user's preferences.  The patent application for
this technology is an interesting read:

   http://www.freepatentsonline.com/20050259828.html

The advantages over existing player piano CD formats seem to be:

  - ability to play the CD on a home stereo and hear the whole
    performance (with piano, and without any "fax machine" tone)
  - ability to dynamically add/remove instruments from the mix
  - increased MIDI expression resolution (255 levels instead of 127) 
  - timestamping of MIDI events for better timing accuracy
  - support for lyric data

Mark Fontana