What is soundtouch?

SoundTouch is an open-source audio processing library that lets you change the speed, pitch, and playback rate of audio independently of one another. Want to speed up a podcast by 15% without making everyone sound like chipmunks? Or shift the pitch of a song down a few steps without turning a four-minute track into a six-minute dirge? That's the kind of thing this handles. Under the hood, it's a toolkit written in C++ that you feed audio through. The classic example included in the project is a command-line app called SoundStretch, where you point it at a WAV file, tell it something like "tempo up 15%, pitch down 3," and it spits out a modified file. As a library, the idea is that developers build it into their own apps rather than end users running it directly, though anyone can grab the prebuilt SoundStretch app for Windows or Mac to tinker with WAV files. The people who'd reach for this are developers building things like music practice apps (slow down a track without changing pitch), DJ software, karaoke tools, or video editors that need lip-synced audio at different speeds. It's the kind of behind-the-scenes component you'd use when your product needs to manipulate audio time or pitch and you don't want to build the math from scratch. What stands out is the platform coverage. Because it's straight C++, it runs practically anywhere: Windows, Mac, Linux, Android, iOS, and embedded systems like Raspberry Pi. There are also wrapper modules for C#, Java, and Delphi, so it's not limited to C++ projects. The licensing is LGPL v2.1, which means you can use it in your app even commercially, with some conditions, and a commercial license is available if you need to avoid those entirely.