Again, take care to avoid breaching any composer's copyrights. Note that the sound of the music depends very much on the quality of the midi player that the user has. Listen to your selected music on a variety of sound cards before embedding the audio since some sounds that sound very good on good sound sources can sound awful on cheaper players. You can use the autostart and loop features as you can with wav files. Please remember to copy to midi file to your site and do not reference another site's midi file directly .
Most systems accommodate simultaneous sound and music.
It is common to want to have a voice introduction announcement followed by music. The difficulty is that it is almost impossible to time the voice and music together. Sometimes it is possible to assume that the music and voice will begin to play at approximately the same time. Using this you can insert a gap at the start of the mid file so that it starts at exactly the end of the voice prompt. This works sometimes but depends on the speed of the link, number of elements downloading and other factors.