The Matrix-1000 was a synth module made by Oberheim around 1986. It is based on the CEM3396 synth voice chip (dual DCO, 4-pole VCLPF etc.). It is 6-voice polyphonic (six CEM3396 inside) but monotimbral.
Many owners report mechanical noise coming from the power transformer. Mine isn't too bad but it certainly is magnetically noisy. The nice harmonic-rich 50-Hz hum can be heard into a bass J pickup from one metre away. The steel enclosure doesn't seem to make much difference.
To adjust your input levels for recording a Matrix-1000, try programs 327, 328, 399, 766 and 909. They are among the loudest. On a Delta 44, 122/163 seems safe (at maximum volume).
The Matrix-1000 has 1000 programs but the program number in a MIDI program-change message (0xC0) is only 7-bit wide. To access program n, set controller #31 to any value above 63, change to program int(n/100), reset controller #31 to any value below 64 and finally change to program n modulo 100. For example, to switch to program 421, send
0xB0 0x1F 0x7F
0xB0 0x1F 0x00
(Assuming the Matrix-1000 listens on MIDI channel 1.)
On the PCB, the voices are numbered 6-5-4-3-2-1 from left to right but voice assignment starts from voice 2 so the first note played after power up is played on the second CEM3396 from the right.
On mine, one of the voices sounds very different from the others (audio). Don't know what the problem is but it is not a bad CEM3396 because swapping them around makes no difference. Interestingly, the fault only affects a minority of programs.
This is http://www.teaser.fr/~amajorel/matrix1000/, last modified 2014-08-18.