I decided to tackle the problem of finding solo music in sound files that contain both solo and non-solo music. Basically, this is a classification problem where each part of a track of music is labeled 'solo' or 'non-solo.' It's an interesting problem because such a classifier would allow you to pull out sections of solo music out of a large pool of mixed music. You might then, for example, attempt to classify the solo instrument.
Part 1: Getting a handle on the problem
Part 2: Strategy
Part 3: Execution
Part 4: Results with test music samples
Part 5: What happened?
Part 6: What next?
Addendum: Wav files, labels, and code