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ChiNo BS.
I personally would not recommend trying play the incidental music at the same time that you are filming... too many problems.
However, most camcorders these days come with composite imputs...for a really low budget way of mixing the sound. Input the music only on 1 speaker....you'll lose that channel of sound but you'll be able still hear it on the other channel...on a mono set it should be a good fake.
Work with what you got. 
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