[yaomtc]

Let's not forget Opus. Not technically patent-free but it practically is. https://en.wikipedia.org/wiki/Opus_(audio_format)#Patent_cla...

Also Vorbis has always been patent free.

[philistine]

Opus and Vorbis are far from useable everywhere. On the other hand, there isn't a piece of software or hardware that won't accept MP3. MP3 is the lingua franca of sound, and should stay that way for a century.