What construction differences between Piano's and Guitar-family instruments contribute to their different sound?
I'm especially interested in the bass notes. Here is what the bass notes on an upright piano sound like:
https://www.youtube.com/watch?v=X1bPQ2z5pec
Very different from the same notes on a bass guitar (acoustic or electric). The piano has a more wobbly, brighter sound. I used to not like the sound of the bass notes on the piano because of this, but now I'm making an instrument for noise music (with a similar range to a bass guitar), and I would like to have a more piano-like sound than a typical bass guitar. It's probably going to be a guitar-like instrument, but it would be nice if I could somehow get a more piano-like sound.
It seems like you get a more wobbly sound on a guitar/bass when you tune down the strings; make them looser. But from what I've read, piano's actually have high tension on their strings. So why do they have such a wobbly sound on their bass strings?
I suppose one reason for their [i]brighter/i] sound is that the strings are struck rather than plucked. But I suspect that there's more to it than that. I found that striking the strings on a guitar with a blunt hard object does give a brighter sound than plucking it with a pick or finger, but not as bright as a piano. Maybe it's because of the more rigid frame that piano strings are mounted on. Piano strings are mounted on a heavy cast iron frame. This is probably more rigid than the neck of a guitar. Maybe the bendiness of a guitar dampens the upper frequencies.
Is there anyone with a decent understanding of acoustics, and the construction of both piano's and guitar-family instruments that can explain why they have a different sound?