123 Synth is a toy piano synthesizer packed full of fun features. The keyboard is modeled on those colourful plastic piano toys we all played with as kids, complete with the number labels on each key. The instrument panel lets you change the keyboard audio, while the drum panel lets you play with a six-piece drum kit. Or you can set the drum kit in rhythm mode and create a custom drum loop! 123 Synth is fun for both adults and kids.
  •    A piano keyboard that lets you play one full octave on the chromatic scale (C to C), including sharps and flats.
  •    An instrument panel that lets you pick from one of six instruments: trumpet, guitar, xylophone, alien sound, violin, and piano.
  •    A drum panel with six pieces: bass drum, snare, hi-hat, small tom, large tom, and crash cymbal.
  •    A rhythm mode that lets you create your own custom drum loop. Tap on the bass drum twice to set the tempo, then fill out the loop with the other drum pieces.
  •    Record and play functions that let you record a song on the piano keyboard, then play it back using any instrument. Or record a song, then play it back as you drum along.
  •    Full retina display support for the new iPad.

123 Synth is built upon the Cocos2D Objective-C framework, and is available for cheap on the iPad App Store.