MP3Gain

Audacity   (Compare Project)

Mostly written in C++

License: gpl

SoX - Sound eXchange   (Compare Project)

License: GNU-GPLv2

Jajuk   (Compare Project)

Mostly written in Java

License: gpl

PureData   (Compare Project)

Mostly written in C++

License: BSD-3-Clause, gpl

LeechCraft   (Compare Project)

Mostly written in C++

License: boost

Rockbox   (Compare Project)

Mostly written in C

License: gpl

musik   (Compare Project)

Mostly written in C++

License: Unknown

Streamripper   (Compare Project)

License: Unknown

Tomahawk Player   (Compare Project)

Mostly written in C++

License: gpl3_or_later

Csound   (Compare Project)

Mostly written in C

License: Unknown