Those things often come together.

I would say most of the things that help the band be successful are not money itself, but the other things that come with it. Student availability for rehearsal (instead of handling child care or working to support the household), transportation availability for after school activities, parents who read to their kids and help with homework (keeps the kids out of remedial test prep).

But still, income level strongly correlates with two parent households. A quick browse of the stats shows that 2-parent households have roughly double the average income of 1-parent households (the math tracks).