Improved pitch detection.
Play a note on your instrument, let Allegro detect the pitch and see where you are on the scale. If the needle points to the left your pitch is lower than the standard pitch, if it points to the right it is higher. In upright position you are in tune.
If you want to run Allegro on an iPod Touch 2nd Generation you need an external microphone. External microphones must be connected before the application is started.