Reaktor is described as 'Native Instruments Reaktor is a virtual, modular synthesis platform. REAKTOR also provides a platform for modular synthesis in the form of Blocks – a range of sound generating and sound shaping modules'. There are more than 10 alternatives to Reaktor for a variety of platforms, including Windows, Mac, Linux, Online / Web-based and Android. The best alternative is Pure Data, which is both free and Open Source. Other great apps like Reaktor are VCV Rack (Free, Open Source), Max/MSP (Paid), Cabbage Studio (Free, Open Source) and PraxisLIVE (Free, Open Source).
Pd (aka Pure Data) is a real-time graphical programming environment for audio, video, and graphical processing. It is the third major branch of the family of patcher programming languages known as Max (Max/FTS, ISPW Max, Max/MSP, jMax, etc.
VCV Rack is a modular synthesizer inspired by Eurorack systems. It acts a host for virtual modules which perform various audio processes. E.G. oscillators, filters, envelope generators, sequencers and more that can be connected freely in almost limitless combinations.
Interactive visual programming environment for music, audio, and media In use for over twenty years by performers, composers, artists, scientists, teachers, and students, Max is the way to make your computer do things that reflect your individual ideas and dreams.
Orca is an Esoteric Programming Language and live-coding environment for musical experimentation. In Orca, each letter of the alphabet is an operation, lowercase letters operate on bang, uppercase letters operate each frame.
Element is a cross-platform, modular AU/VST audio plugin host. Create powerful effects racks and instruments by connecting plugins to one another. Load graphs on the fly for quick access to your sounds.