I found by experiment that the CDP-130 does not use the standard General MIDI patch numbers. Instead it uses its own 10 tones in the order in which they are printed on the keyboard, i.e.:
0 = Grand Piano 1 (same as GM)
1 = Grand Piano 2 (similar to GM's Bright Acoustic)
2 = Electric Piano 1 (similar to GM's Electric Grand)
3 = Electric Piano 2 (sort-of similar to GM's Honky-Tonk)
4 = Electric Piano 3 (similar to GM's Electric Piano 1)
5 = Harpsichord (very different from GM's Electric Piano 2)
6 = Vibraphone (very different from GM's Harpsichord)
7 = Strings (very different from GM's Clavichord)
8 = Pipe Organ (very different from GM's Celesta)
9 = Jazz Organ (very different from GM's Glockenspiel)
and any other patch number results in Grand Piano 1.
As you can see, patch numbers 0 through 4 are similar to General MIDI, but patch numbers 5 through 9 are not. For example, some General MIDI files of Baroque music (Bach, Scarlatti etc) try to set patch number 6 to get harpsichord, but this results in a vibraphone sound on the CDP-130 unless you change the number from 6 to 5.
