When do You Need a Mechanical License?

https://www.harryfox.com/license_music/why_need_mechanical_license.html

If you are manufacturing and distributing copies of a song that you do not own or control, you need to obtain a mechanical license. This is required by the U.S. Copyright Act, regardless of whether or not you are selling the copies that you make.

Under the U.S. Copyright Act, the right to use copyrighted, non-dramatic musical works in the making of sound recordings, including CDs, records, tapes, ringtones, permanent digital downloads, and other digital formats (e.g., interactive streams) for distribution to the public for private use is the exclusive right of the copyright owner. However, the Act provides that once a copyright owner has recorded and distributed such a work to the U.S. public or permitted another to do so, a compulsory mechanical license is available to anyone else that wants to record and distribute the work upon obtaining a proper license and subsequently paying royalties at the statutory "compulsory" rate as set forth in Section 115 of the Act and the related regulations. In other words, if the song has already been recorded and commercially released, you can record and distribute it as long as you obtain a license and pay royalties.

You don’t need a mechanical license if you are recording and distributing a song you wrote yourself (and you haven’t assigned the publishing to another party), or if the song is in the public domain. If you are not sure if the song you are looking to license is in the public domain, you can search for the song on:

www.pdinfo.com
www.pdmusic.org