Sequential Circuits debuted the MIDI standard in 1982 with their Prophet 600 synth.
The first interface was released by Sequential the same year for the Commodore 64 computer. The Yamaha CX5M was the first computer designed for music, and it used the Sony MSX computer.

It really caught on with the Atari ST computers because the owner of Atari's son had the bright idea of including MIDI on the ST.