Midi sound quality depends on the soft synth you are using. If you are using the Microsoft default it will sound a bit ropey and you would get better sound with another synth. Sadly the TTS1 is not available as a free download any more but if you buy BIAB 2025 you will get - I think - VSTSynthFont free which with a decent GM sound font like Timbres of Heaven will sound much better.