YouTube Audio Library
YouTube offers great, free, high-quality audio and music files to use in your next design and development project, such as a video, a website or an app.
Related Tools

Sounds Crate
Sounds Crate offers fully mastered audio tracks for your productions that you won’t find anywhere else. No attribution required.

Converse Sample Library
The Converse Sample Library is a growing collection of audio samples, all samples are completely royalty free – no strings attached.

Bensound
Bensound is a great source for royalty-free audio and music tracks to use on your next video or audio project.