DigiTech Midi Implementation Manual page 118

Global link table of parameters to continuous controllers (P2CC)
All parameters in the GSP21 are assigned a parameter number. This number is
used as an offset into the P2CC table. The value of an entry in the P2CC may
be 0 through 129. 0 - 127 correspond to continuous controllers 0 - 127. 128
is Channel Pressure and 129 is NotLinked. The following table lists the
GSP21 parameter number assignments and shows the correspondence between a
byte in the P2CC and a GSP21 parameter.
1 Not Used
2 Compressor
3 Compression Amnt
4 Distortion
5 Distortion Type
6 Distortion Balls
7 Graphic EQ
8 GEQ 64Hz Band
9 GEQ 160 Hz Band
10 GEQ 400 Hz Band
11 GEQ 1.0 kHz Band
12 GEQ 2.5 kHz Band
13 GEQ 6.3 kHz Band
14 GEQ 16 kHz Band
15 Master Volume
16 Enhancement
17 Noise Gate
18 Gate Threshold
19 Not Used
20 Chorus
21 Chorus Delay
22 Mix:Chorus R Lvl
23 Mix:Chorus L Lvl