Apps with 'Synth rack' feature

FL Studio (originally known as FruityLoops) is a full-featured Digital Audio Workstation (DAW) offering a complete range of professional tools for everything from audio editing and beat creation to advanced arrangement, composition, mixing and mastering.

Reason is a virtual studio rack with all the tools and instruments you need to turn your ideas into music. And it's more than just a set of excellent synths and effects. It's a complete music system. Step into the age of Reason.