Wise Metronome: Kangaroo

This metronome app measures user's play speed by recording audio and analyzing in realtime. Advantages:
- shows if user is playing slower or faster than the set BPM
- update the set BPM using the measured BPM
- shows statistics (average and variance)
- auto mute: no beat sound while user is playing at correct speed
- auto quiet: reduce beat volume when user pauses playing

Also provides an alternative beat visualization to the ubiquitous pendulum for kids: kangaroo.

Of course, this app has basic features:
- set BPM with tempo name explained
- change beat sound, using pre-recorded data or synthesized sound with adjustable frequency
- set first beat emphasis for 3/4 or 4/4
- change beat volume and background color

Limitation: since it relies on distinct peak and sustain of volume over time, works with piano but not with violin, etc.