Muller Monthly Music Meta | 2017 Puzzle 7: “Let’s Do It A Cappella!”

2017 Puzzle 7: “Let’s Do It A Cappella!”

Here’s contest puzzle #7. Solve using the Crossword Compiler applet below, download a PDF, or use Across Lite.
The meta is a type of musician.
Submit your answer to the meta using the form on the home page.

Let's Do It A Cappella! by Pete Muller