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tracks from the local collection". The SimilarFingerprintBias is
implemented in the SQL plugin and registered with the DynamicPlaylist
system.
So the query can happen directly in SqlCollection.cpp, you don't even
need to use the QueryMaker unless it would be easier to implement.

Once there is a second collection that implemented fingerprints you
can think of creating that capability. That would mean that the
Dynamic Playlist system already supports selecting the source of the
tracks. I do also have the suspension that those implementations  will
inevitably have to depend on GTACFeat, since there is AFAIK no
standard format for audio fingerprints or it's not useful in this
context.

The FingerprintCapability on Track makes sense, I have no issue there.