How to tag different sources?

[simoncn]

(30-01-2014 20:43)iqt Wrote:  I'm using Kid3 on OS X (coming from Linux).

I don't think anything else apart from Kid3 maps SOURCEMEDIA to TMED. Normal practice (if this tag is mapped) seems to be split about 50/50 between MEDIATYPE and MEDIA. If forced to make a choice, I would probably choose MEDIA. You could then use aliasTags to remap MEDIA to SOURCEMEDIA.