Beast is described as 'digital synthesizer and music creation system, released as Free Software under the GNU LGPL-2.1+' and is an app in the Audio & Music category. There are five alternatives to Beast for Mac, Windows and Linux. The best alternative is Pure Data, which is both free and Open Source. Other great apps like Beast are Reaktor (Freemium), Max/MSP (Paid), ORCA (Free, Open Source) and Automatonism (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.
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.
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.