slk486 is correct, the SB16 mpu implementation is only a basic one and stuff that rely on roland's extended features will fail.
BUT
some days ago SoftMPU was released
here , it is not a 100% solution but it makes some stuff that were failing on non-Roland mpus to work , have a read at the vogons thread
Good choices for a Roland mpu are the following roland cards (lol):
SCC-1 (mpu + scb55 synth)
MPU-401
MPU-401AT
RAP-10 (mpu + sc-7 synth)
LAPC-I (has an mpu but who cares, it's an extended mt32 itself)
there are other makers of compatible mpus like MusicQuest , but I have no real knowledge of them...
also here is a schematic for a SB->midi cable:
more info here:
http://web.singnet.com.sg/~lau0cy/sb.htm