I want to play videos in iTunes faster (1x, 2x, double speed, etc.) or maybe slower. How do I do that?
Right click on the file in iTunes and choose "Show in Finder." Then right click the file and open in Quicktime Player. In Quicktime Player you can choose the playback speed by using the A/V Controls (Command + K or Window>A/V Controls). From there, you can select the playback speed:
Alternatively, you could use VLC or another music player.