Probably 10K will do!

But, here are the specs from the transistor I picked.

I'm not sure which of these figures is gain, but I think it is HFE@1c/VCE

min: 100
max 250
mA -150
V -2

In case not, we have VCE(sat)
Max V -.5
@IC (mA) -500
@IB (mA) -50

Also, PIC will be running on 3.7V same as sound board.

Bart