Midimeow is an easy-to-use tool to converts on the fly:
Midi to Mp3 at 128 Kbps and 196 Kbps
Midi to Wav
Midi to Ogg vorbis
It allows to change the rate of the output (3 rates available)
The number of channels (mono or stereo)
And if you want the volume of the output instead of the presets using the built-in
interface to change mixer's settings.