Definition
Mechanical Royalty
The royalty owed to songwriters and publishers every time a composition is reproduced — physically, digitally, or via on-demand streaming.
Mechanicals originate from the era of mechanical reproduction: pressing a record was a 'mechanical' use of a composition, and the songwriter was owed a per-copy fee. The same principle now covers downloads and the reproduction component of interactive streams.
In the US, statutory mechanicals for streaming are administered by The MLC (Mechanical Licensing Collective). Outside the US, it's the local society (MCPS in the UK, GEMA in Germany, SACEM in France, etc.).
The current US statutory rate for streaming mechanicals is set under the Phonorecords IV proceeding — roughly 15.35% of service revenue allocated to songwriters, distributed via the MLC.
If you wrote the song, you're owed mechanicals. If you only performed on the master, you're not — you're owed master-side streaming income instead.