Blip Synthesizer is a fun app that doesn't require musical knowledge to play.
The interface is a grid where each row is for a note in one octave, and each column represents notes in a pair of 4-beat pattern in a loop, and each column contains 8 polyphonic tones.
Use the slider at the bottom to alter the playback speed - it will display the tempo.
You can add and remove notes, change scales, change tones, all while music is playing.
Cheap Synthesizer Roundup
Changes in v1.2
- Add a list of preset sound (Simple Tone, Chine and Harmonica)
- Improved preference screen