The ZX Spectrum 128 and the amstrad's Spectrum range (+2 and +3) also feature a Midi compatible port thanks to their RS232/Midi port.
Of course Amstrad's ZX spectrum +3 is a clever choice as it include Disk drive.
MSX often featured such a Midi port, and were featuring a wide range of sound processors/co-processors :
*MSX 1 : General Instrument AY-3-8910 soundchip