Developer Duncan Smith released Audio Lab on Android as a music visualizer that tries to offer some tools for detecting beat and pitch.
Audio Lab iTunes Description:For music fans, add some colour and great visuals to the experience with Audio Lab. It offers volume, pitch and beat detection.
Watch the balls bounce off each other in Mosh Pit, explore alien worlds with World Explorer, be dazzled by the explosions in Flocking, bop to the beat with Beat goes on, Rainbow and Leafy ... or just chill to some colourful clouds.
You can get to options and controls by swiping in from the right side of the screen. Touch the main screen to make it disappear.
Controls include -
Previous / next song
Pause, which stops the microphone input
Export to csv, which saves the current frame of data to a file
Display shows the current visualizer
Each tool / visualizer may have it's own separate options.
There is a selection of tools as well as the playful visualizers. Tools include -
Input, shows the original sound wave.
FFT shows the resultant frequency wave.
dbFS shows volume across frequency's.
Notes displays recognised notes. Great for singers to show what notes they are hitting
Beat detection shows BPM. This is calculated over time. It could be used by drummers to try and hit a constant BPM ... and then improve their score.
Note that the app uses microphone input that can detect external music being played, but it's at it's best when music is played via the same device.