You didn't mention it, but there is a scan of the service manual on your web site, which you linked. Kinda hazy but better than nothing.
You get high hats but not the others? First the service manual has a good theory of operation section which explains it pretty well, plus the block diagram. But to isolate the problem, does the start/stop switch function? Does it make the hi hats stop and go? If so, then the flip flop is working, and that is your 4011. Also, does the tempo control affect the speed of the hi hats?
As to the other sounds, they are all triggered from the memory chip, so are there output pulses from pins 12, 14, 16 of that IC? If not, then the voice circuits won't make sound.
Since you do get hi hats, I assume the noise generator is working.
If there are control pulses leaving the memory, look at each sound output transistor for signal. Those mostly have to run through the accent circuit, so if it has an issue, you might lose them.
Someplace to start anyway.