You have to get an .mp3 encoder. Something like Ffmpeg will convert .wav to .mp3 (iTunes should be capable of doing that too). As for .mid to .mp3, the way I do it is to go through a .mid sequencer that will convert the .mid data to .mp3 as you export the song. Of course, sequencers are useful mainly if you are a musician IMO, so maybe there's another way.

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iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

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