Synthesine is described as 'web playground for synthesizing sound waves from scratch. You can use it to create sine waves, white noise, and other building blocks of sound, and then pass these through modular components to synthesize more complex sounds like bells and whistles' and is an app in the Audio & Music category. There are more than 10 alternatives to Synthesine for a variety of platforms, including Windows, Online / Web-based, Mac, Self-Hosted solutions and Linux. The best alternative is SuperCollider, which is both free and Open Source. Other great apps like Synthesine are Sonic Pi (Free, Open Source), ChucK (Free, Open Source), Nyquist (Free, Open Source) and Faust (Free, Open Source).
A real time audio synthesis engine, and an object-oriented programming language specialised for music. SuperCollider was created in 1996 by James McCartney, Since version 3 it is released as free software.
Soinc Pi is a live-coding audio software. Learn to code creatively by composing, improvising or performing in an incredible range of styles from classical through to algorave. FEATURES Simple enough for computing and music lessons.
Nyquist is a language and IDE for sound synthesis and music composition. It is implemented in C and C++ and runs on Win32, OSX, and Linux. Nyquist combines a powerful functional programming style with efficient signal-processing primitives.
Faust (Functional Audio Stream) is a functional programming language for sound synthesis and audio processing with a strong focus on the design of synthesizers, musical instruments, audio effects, etc.
The SOUL platform is a language and an API. The language is a small, carefully crafted DSL for writing the real-time parts of an audio algorithm. The API is designed to deploy that SOUL code to heterogeneous CPUs and DSPs, both locally and remotely.