ofxAudioDecoder is an openFrameworks wrapper for libaudiodecoder
On OSX it can load .mp3, .m4a, .wav, and some other formats. Instead of being used for playback, it's meant for analysis. Because libaudiodecoder also supports Windows, with the addition of the Windows-specific sources and the creation of a Windows-specific project file ofxAudioDecoder should also run on windows.
The example project loads a file demo.mp3 from the data/ folder and draws the left and right channels into an ofMesh. You may drag and drop a file onto the OF app to load it and render the waveform.