That's difficult. Normally MIDP1 is (at least should be) ready to play WAVs. Just think of "Sound.FORMAT_WAV".
But it is not true. It won't. MIDP1 is used only with tones (beeps). I had a 6220 and tried for weeks to play anything else than a tone, but nothing. Asked in a lot of forums, but nothing.
Now I got a 6230 with MIDP2. It still won't play WAVs in apps, but it plays MIDI files.
I think, you should use tones. They are terrible to listen to and are sometimes annoying, but this is the only way.
With MIDP1 you cannot use multichannel tones. Just think of the old LCD watches with 7 music, or the old LCD hand held games...