Hi Ken,

I almost always use a Bb single row, and F-Bb-Eb triple row. I have done so for a very long time.

It's not so much about which songs have been recorded using those keys, but there are a huge number of them.

It is often the case that a particular recording might have used other key accordions. Many songs use a C single row, or G-C-F triple row. But that's not a problem - just play it in the key you want to use.

I often learn a song by ear, by playing along with an original recording. If the recording isn't in the key I want to play it in, that's OK, because I use a some apps that can change the key of the recording to match what I want to play it in. The best known app for this is Amazing Slow Downer. As the name implies, you can also change the speed of the playback, which VERY helpful to pick out the notes more easily.

I use Amazing Slow Downer as a desktop app, but for mobile I use Anytune Pro+.

-David