You can search for arbitrary songs with most extensions and I believe this includes mopidy-soundcloud. You must have used something much older than v0.18 as it

You can search for arbitrary songs with most extensions and I believe this includes mopidy-soundcloud. You must have used something much older than v0.18 as it was released about a month ago and needs no more configuration than any other media player i.e. where's the music. Finding a an MPD client that works how you want is the tricky bit.