media_tune(var handle,var volume,var rate,var balance)
Changes the volume, speed and audio balance of a media stream.
||the stream handle that was returned by media_play or media_loop.
||the new volume (1..100), or 0 for no change. The overall media volume can be changed by midi_vol.
||the new playing speed or sound frequency in percent, or 0 for no change. For instance, give 100 for normal speed, 50 for slow motion or half frequency, or 200 for double speed or double frequency.
||the new tone balance (-100 .. +100), or 0 for no change. Negative values shift the sound towards the left speaker and positive values towards the right speaker.
// Play "silent.mpg" at half speed