Here is a list of the MIDI channel assignments for the GW-8:
MIDI - Part Name
1 - Accompaniment 1
2 - Accompaniment Bass
3 - Accompaniment 2
4 - Upper Part
5 - Accompaniment 3
6 -
7 - Accompaniment 4
8 - Accompaniment 5
9 - Accompaniment 6
10 - Accompaniment Drums
11 - Lower Part
12 -
13 -
14 -
15 - Melody Intelligence
16 -
MIDI - Part Name
1 - Accompaniment 1
2 - Accompaniment Bass
3 - Accompaniment 2
4 - Upper Part
5 - Accompaniment 3
6 -
7 - Accompaniment 4
8 - Accompaniment 5
9 - Accompaniment 6
10 - Accompaniment Drums
11 - Lower Part
12 -
13 -
14 -
15 - Melody Intelligence
16 -