There are two things that I would like to touch upon with this subject. One was sort of brushed on by Dave Mudgett about mass and density of the metal that the strings are in contact with.
The other is tuning length and string gauge. These two factors without a doubt change the tone of a guitar.
I sort of learned early in my musical career that if I was going to make enough money to support a family and purchase a home, a full time musical career was not the way to go. So, I went to welding school and became a welder then a business owner of a welding company. Throughout my career I learned a great deal about steel and its structure.
In short, high tensile carbon steel has small amounts of nickel, carbon, manganese and so on. Each of these different combined metals make the steel harder or softer. You all know how lead crystal sustains its vibrations when tweeked with your finger; well, high tensile carbon steel will do the same thing if you tap it with another piece of metal. It just rings on and on and on. If you were to cut a twelve inch pancake circle out of high tensile steel, (for the steelers in here who know this stuff, SA 516 Gr70) hold it in your hand and tap it with a hammer it rings like a bell; however, if you hang that same piece of steel off a piece of wire and tap it again, the sustained ringing lasts almost 70% longer.
For this reason, on the higher quality guitars, most bridges and nuts and tuners are made out of high tensile carbon steel. Those steel guitars that do not use high tensile steel for the nuts, bridges and tuners will most definitely not get the same tone or sustain.
To the point above, hanging a the high tensile steel circle on a piece of wire extends the ringing: I have often wondered what would happen if somehow the bar area that touches the strings was isolated or insulated from the players hand, what would it do for the sound of the strings.
High tensile carbon steel strings????
Nope, it couldn’t work!------------------
(I am not right all of the time but I sure like to think I am!)

). They each will produce a painting that exhibits a different style, with factors at play such as width of brush strokes, amount of paint used, shading, and general betrayal of influences. However, each and every one of the paintings will still be......blue.