SoundBox is described as 'tool for composing synthetic music, in your browser. Its design is basically that of a music tracker, which means that the music is organized in tracks and patterns'. There are more than 10 alternatives to SoundBox, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac, iPhone and iPad. The best alternative is OpenMPT, which is both free and Open Source. Other great sites and apps similar to SoundBox are SunVox (Freemium), MilkyTracker (Free, Open Source), Renoise (Paid) and Schism Tracker (Free, Open Source).
VividTracker is a true Amiga Protracker compatible music tracker for iOS. You can load, edit, save, or create new Amiga modules. It comes with support for AudioCopy, which means you can copy samples from other great apps such as Korg iMS20, Animoog or Propellerhead’s Figure.