To get Timidity++ music working in DOSBox games, apart from also setting up with the mixer and config commands, select General Midi for music at port 330 whenever you're in a sound setup for whatever game. Tried this with DOOM setup, and the results are awesome.
Only noticeable thing with Timidity in DOSBox, is the extra lag/load times, but it shouldn't be that bad to deal with.
Instead of playing MIDI's in Winamp, use the Timidity++ MIDI Player. It should be the timw32g.exe file.