This can be easily and quickly done in the playback control of SmartPlaylist, which can be accessed from anywhere, at any time with "♬":
You can use this new feature
- just for fun
- to scan for a specific playback position
- for quickly going through MP3-lectures at 1.5x or 2x playback speed
- to play along at a slower speed for practice
- This only works with iOS 6 (not iOS 5)
- On the iPhone / iPod the control is only available in portrait mode, but not in landscape mode (there is not enough space in the pop-up). On the iPad it is available in both modes.