MC,
This means if one MP3 file is playing and you select and play the next, the first one stops completely and the 2nd one starts instantly.
However, if you have some space at the start of the 2nd MP3, this 'space'/quiet will be heard before the file starts playing.
However, when you crossfade between Wave/Midi files, the first file fades out in volume while the 2nd one fades in (with a momentary period where you hear both files playing at the same time!)
Hope this helps.
Thanks,
AJ