Most if not all of artists sing and play an instrument at the same time. Now we have to create the relationship "artist-recording" twice, with the attributes "vocal" and "instrument" separately. It is very inconveniently and take much time.
I'm ready to make 1000 relationships for 1000 Jerry Lee Lewis' recordings (vocal+piano), but I'm not ready to make 2,000 ones (1000 vocals + 1000 pianos) .
It would be very useful to combine the addition of both attributes during a relationship creation. A simple small square "Vocal" would be enough for the most cases, without any specification like "Solo" or "Contralto".