My take on an NSView subclass that can display the waveform for an audio file, allowing customisability of colors, play/stop control and image generation (from the view).
I'd recommend looking through the code and adapting/modifying to suit your needs.
Note If you're looking for an extremely accurate high performance visualization of a sound file or live sound recording, there are most likely alternatives that would better suit you.
WaveformView is a general-purpose waveform view to visualize a .wav file.
LiveWaveformView will show a live waveform for a given AVAudioRecorder.
HybridWaveformView is a hybrid/combination of both of these - it's a bit experimental and not perfect. It should display a rough "live" waveform, then switch to an accurate waveform once recording has stopped and the sound recording files has been saved and loaded.