This is an article culled from archive material, circa 1997.
The
D-550 is a 2U-high, 15.5" deep rackmount
Roland D-50.
The
functionality is identical, although D-550's are generally more recent
than D-50 keyboards and will probably sport a later firmware release,
offering slightly improved MIDI features. Programming via the front
panel is slightly more tedious than with the keyboard, since there is
no joystick or data entry slider, and no soft buttons under the
display.

The
PG-1000 is the dedicated programmer
for the D-50 and D-550. Unlike
the PG-800 for the
Roland MKS-70, it works by MIDI
system exclusive, and requires an
external 9V power supply. It has no less than four MIDI sockets: data
to the MIDI In is echoed to the MIDI Thru, and also merged with
locally generated sys-ex and sent to the D-50/D-550 on the MIDI
Out. The parameter in socket allows patches to be downloaded from the
D-50/D-550's MIDI Out for editing.
The PG-1000 sports an impressive number of faders, but many are in
fact overloaded several times for each patch's four partials, two
tones and one common parameter block. Even so, programming is fairly
easy, since parameter values are displayed in the backlit LCD, and
there are dedicated partial/tone select buttons.
There has been talk, on the
Max
mailing list and elsewhere, of
using the PG-1000 as a generic fader box. This is possible, to an
extent, and only requires a sys-ex parser to interpret the fader
output, but since the fader functions are specific to the
synthesiser's parameters they have specific ranges (0 to 10, 0 to 127,
and many others). Such a restriction is not necessarily a bad thing,
of course...
D-550's are rather hard to find, since rackmounts tend to stay put in
studios and live rigs, but a D-550 in good condition (especially if
you can find a PG-1000) is certainly worth owning.