This is probably the best SPC player of them all. It has a myriad of features: speed/pitch change, channel mute, echo disable, DSP pitch/volume registers, etc.
Use the left and right arrow keys to toggle the data viewed during SPC playback.
v2.17.7 (build 5616) (2016/08/27)
This updated version of spcplay fixes the pitch modulation amplitude (for example, FF6 Kefka's laugh).