Analyze Sound file C++

I am trying to write a node.js module that will let me take an mp3 and separate the rhythm and the melody. Are there any c++ libraries that will let me do this or does anyone have any ideas where to start? There's a node.js library that will analyze and display the waveform of a sound file, so I'd like it to be like that except produce two tracks, one as the melody and one as the rhythm.