I'd be happy to see the following ensembles for recording–performer relations:

• piano trio (= piano, violin, cello) (e.g. Beaux Arts Trio)
• piano 4-hands or "piano duet" (i.e. two pianists on the same piano)
• piano duo (two pianists on two pianos) (e.g. Duo Tal & Groethuysen)

Other ensembles seem less interesting since I don't think a lot of group artists exist for these configurations. If later we add an instrument-work link, that might become useful

• piano + violin
• piano + cello
• piano quartet (piano, violin, viola, cello)
• string quintet (2 violins, 2 violas, cello)
• string sextet (2 violins, 2 violas, 2 cellos)

@reosarevok, your opinion?