This section may be of interested to the musicians / audiophiles of you.
While MIDI versions may not sound as authentic as the SPC format, the advantage is
that if you have a notation / compositional program, you can view the musical score,
listen to individual instrument tracks and change the tempo.
Handy stuff if you actually want to learn a certain melody on your own instrument - You can listen to an individual
instrument in a song on it's own and slow it right down to learn it.
The good news is that ZSNES allows you to mute / unmute individual instruments of the current song actually playing in-game (using the F5-F12 keys), and you can assign speed up / slow down keys to alter the tempo as well.
Even more conveniently is that SnesAmp allows you to do that within Winamp itself with the .SPCs!
The SnesAmp 'skin' can be activated by going into Options / Preferences and selecting the SnesAmp plugin and clicking Configure.
Select the 'Other' tab, tick the box that is labelled 'Display the control dialogue' and press Apply / OK.
Back in Winamp, it's best to have the whole folder of songs loaded in the playlist window so that when the SnesAmp skin is activated you can still change tracks and play/pause.
Selecting an SPC file and playing it should automatically change the main WinAmp window to the SnesAmp 'skin'. To go back to normal, Right-click somewhere in the purple logo on the side and select Disable. Unfortunately you have to go through preferences and configure if you want to activate it again.
Note: SnesAmp may come up with a message when you deactivate it, saying it can be reactivated by going to the plugin configuration under the 'Mixing' tab. This doesn't seem to be correct, at least not in the version I have. Instead, it is under the 'Other' tab.
If the SnesAmp window doesn't seem to activate when you play a file, try exiting and reloading Winamp, and double-check that the box is ticked in the plugin's config.
Just keep in mind that this won't work with the .MP3 versions, or with any other audio format you may convert the songs to. So don't go deleting the SPC's just yet!