Pixitracker is a simple, pixel-based sample editor and chiptune tracker that's designed to be fun to play with, so it doesn't have the hardcore (and intimidating, I'll admit) tracker interface. Pixel-based means that you specify notes and patterns by turning dots on and off by clicking on them. Designed so you can just mess around with it. Record patterns, make new samples and export them as .wav files, record sounds. MIDI aware so you can plug your favorite MIDI device in and use that as the UI. Supports multiple audio drivers, too. There are versions for Apple iOS, Android, Windows, OSX, and Linux. Samples are delineated with Space Invaders-style sprites so you can tell them apart.