You can't learn from any project if you are not excited by it, no matter how small. Purely for learning this should be the approach:
1. Understand what you like. Look for similar project which is successful.
2. Download the oldest public version of the project and understand that.
3. Follow the subsequent versions and understand what changes were incorporated into them.
4. Join the newsgroup/irc relevant where this project's developers hangout and follow their posts.

There are two things you need to learn. One is syntax and approach to problem solving. This looks tough but will be easy once you get into it. Second is the group's dynamics and culture. Which might look easy from the outset but might prove to be tough once you get into it.

Thats bad. Your boss has no say in how you code but if it performs, scalable, extendable, secure and follows teams' coding norms.

I for one though don't like listening to music while coding.