Does GoldWave support mp4, m4a, mov, or aac files?

Installing the QTFile plug-in will allow GoldWave to open (but not save) those files, provided they are not copy protected.

GoldWave supports these files provided you have QuickTime or iTunes installed. Files can be opened and converted, but cannot be saved yet. You will have to save an edited file in a different format. Note that m4p files are encrypted and copy protected and cannot be opened (see the question above), but they can be upgraded in iTunes.