I normally play about 90 percent styles. When I do use SMF ( or audio tracks ) here’s a few reasons why that come to mind:

1. Two handed parts can be played, especially rootless and more complex extensions that aren’t typically recognized with auto accompaniment.

2. I use SMF for songs that have very important baselines, drum parts, breaks, or too many parts for me to comfortably cover.

3. Sometimes I cover songs that for the most part are in 4/4 timing but will have an odd time measure here or there. For example, the chorus of “ I Say a Little Prayer for You” has a 3/4 measure in the middle of a phrase.

4. I also play chromatic harmonica on some songs and to use both hands to do so.

5. Sometimes I run into a song where I can’t find a style that seems suitable.

6. Some songs have ritardando, accerando, or sudden dynamic changes which are hard to do with auto accompaniment.

If I had a keyboard with a chord sequencer, I’d probably use less backing tracks than I do now.

I do have a lot reasons why I generally use styles over SMF, but maybe we’ ll leave that for another thread?