Feature requests: How can we improve the Musicalion.com experience?

Detailed search would be more helpful, if the "exact" mode would not only allow inclusion of instruments but also exclusion.

E.g. searching for duetts sopano/bass and arbitrary accompaniment I get the following search results:
- Without "exact" all works for terzet,quartett, etc, so the duetts are very hard to find amidst the plenty of results.
- With "exact" I only get a cappella compositions

What I would like is to exactly include voice solo soprano and bass, to exactly exclude all other voices and get duetts a cappella + duetts with pianoforte + duetts with lute + duetts with guitar + duetts with .....