Thanks for reading :) I remember Ruth Clark in "Building Expertise". Here's some of the sources she cites:

- Moreno, R., & Mayer R.E. (2000a). A coherence effect in multimedia learning: The case for minimizing irrelevant sounds in the design of multimedia instructional messages. Journal of Educational Psychology, 92(1), 117–125.

- Gibbons, C. (2007, December 29). Professionals take work out of their workplaces. The Arizona Republic, D1.

- Kenz, I., & Hugge, S. (2002). Irrelevant speech and indoor lighting: Effects of cognitive performance and self-reported affect. Applied Cognitive Psychology, 15, 709–718.

- Ransdell, S.E., & Gilroy, L. (2001). The effects of background music on word processed writing. Computers in Human Behavior, 17, 141–148.

The studies here seem to suggest most people learn better in quiet most of the time.

That said, I listen to music without lyrics myself while learning :)