From MusicBrainz Wiki

What should and shouldn't be merged together? (addition)

A recording is intended to represent unique audio. This means you:

shouldn't merge recordings from a different media types (Vinyl, CD, SACD, DVD-V, DVD-A, digital media, etc.) and/or with a different number of channels (mono, stereo, multi-channel)

--RocknRollArchivist 07:14, 6 May 2012 (UTC)