> if a perfectly symmetrical interior (& exterior - anything contributing to resonances) wouldn't sound better

I'm guessing it would likely look more pure on a frequency plot, but sound sterile if things were perfectly symmetrical. The little imperfections, materials, and design tradeoffs give each instrument its unique tone color (timbre). Often, musicians will chase a certain builder and year, and even within that, only a few instruments will be considered "great". For example, guitarists chasing the perfect Les Paul or most classical violinists chasing a Stradivarius.

In acoustics symmetrical and parallel surfaces lead to what are called standing waves, which heavily emphasizes specific frequencies. For the most part in things that are musical (instruments, recording studios) you don’t want that. Except of course where that’s the whole point, like the heads of a drum.

There’s a lot more subtlety to it, but in general, variation will produce richer more complex timbre.

Yes, but I suppose the general shape of a violin, curvy, pinched waist, bowed top and bottom surfaces, already avoids those kind of overly simple/concentrated resonances. On a side note, I wonder how much changing any of these shape factors affect the sound? Which are most critical? What happens without the pinched waist, or if it is made even narrower?

Interesting mix of wood too. The 1619 viola has a very tight grain spruce top and the maple back has a beautiful curl. Same with the 2019 Beilharz cello and the 1785 Storioni violin – the curly maple really shows. The back on the 1705 Goffriller cello seems very plain on the other hand, and suprisingly so does the 1717 Stardivari's. The 19th century Hopf violin has nice curly maple, but the grain on the top seems extremely loose. Any idea how do these compare musically? And does someone know if Stradivarius ever used curly maple and when curly maple was first used for musical instruments?