For practice and performance I often use custom rubato, or "free play" type custom styles. There is no drum percussion or bass "groove." In many cases I'll activate sync stop, so the sound fades when I lift my fingers from the keys. I suppose it's more like organ playing, except that the arranger still adds a bass note, and I don't have to press all the keys to play a chord. Some of my friends feel that the resulting sound is more authentic, and certainly less busy than full accompaniment. Besides, this is the only way I know of to play liturgical music and traditional hymns.

I'm not a fan of playing over SMFs, MP3s, etc. Maybe with liberal use of mark & jump, muting parts at certain times, tempo changes, etc., it might be ok. But it begs the question- how much should I do in advance? I like arrangers and other auto-accompaniment instruments because I want to interact with the songs I like more directly than just making an mp3 playlist, or mix tape (remember those!)

But- for a short while I belonged to a casual singing group. I'm hardly a great keyboard player, and I wanted the emphasis to remain on the singing. So for practice and performance we used customized SMFs and KAR files.

Fran, I thought MIDI and Karaoke files were the same thing, except with a different extension? What are CDG?? Using my little BK-7m, I was able to change the key several steps, apply covers, makeup tools, change tempo and display the lyrics. Awesome tool! On .mp3's I could change the tempo and wash out most of the vocals with Center Cancel. Not sure about changing the key on .mp3s. Karaoke files were much more flexible. So each has it's purpose!