What are some alternatives?
When comparing AudioKit Synth One and us.openlabs.com Stagelight, you can also consider the following products
Sampulator - Make (and record) beats on your keyboard
LMMS - Make music with a free, cross-platform tool
Ableton - Music production software and hardware.
Cakewalk - The next generation of SONAR, the world's finest and most powerful DAW - now FREE.
Splice Beat Maker - Make and share beats in your browser
Reaper - Reaper is a focused digital audio workstation (DAW) developed by Cockos. In the creation of the software, the digital audio technology company intended to make audio editing accessible to the masses.