Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
OnlineSequencer.net - OnlineSequencer.net is an online music sequencer that allows users to create beats and music tracks.
Adobe Audition - Mix, edit, and create audio content in Adobe Audition CC with a comprehensive toolset that includes multitrack, waveform, and spectral display.
GoatTracker - This is a crossplatform C64 music editor.
GarageBand - GarageBand is a fully equipped music creation studio for Mac
Jummbox - A modified Beepbox that have more stuff then Beepbox. It can be used just like Beepbox. The features of Jummbox is the same of Beepbox's features, but Jummbox have more stuff to offer.