If you take a dozen different recordings of acoustic stringed instruments and find violins sound more like violas you can safely predict your system needs work.
Or the opposite, where violas have lost their lush bodies and sound more like their smaller cousins.
It's consistency that helps us get our systems to sing the right tune, and that tune doesn't have to be built from violas and violins. It can be any authentic instruments you are familiar with, like voice or guitar.
Which is why we don't adjust our systems to get one track just right at the expense of others. A wide variety of musical choices played at appropriate levels helps balance the system setup. Bass plucks needn't all thunder nor sound like they are without body. A carefully chosen set of music displaying a decent variety of recordings and instruments is essential to getting the system properly voiced.
If your system only sounds good on small ensembles or big rock bands, you might consider venturing out into change.
Violas and violins should sound like themselves on any system worth its salt.
