Yeah, it is interesting. But I think the differences are small and don't
make too big a deal out of them, but be realistic.
For classical guitar I like a cedar top with rosewood back and sides. For
acoustic, I like spruce on mahogany or rosewood (though my current acoustic
is cedar on rosewood). For electric guitar I don't really think the wood
matters that much, and I also can't tell much of a difference in the
strings. Strings on acoustic matter, as a regular bronze string or phosphor
bronze string has more overtones and an airy ring to it than some others,
but I've been using nickel flats on my acoustics for a couple of years now,
because they last forever, whereas bronze strings lose their zip after a
few weeks of play.
On harmonica... I don't think the differences are huge by any stretch of
the imagination, especially if you're playing amped with distortion, I
don't think there's a difference at all. And I can't tell a difference
between coverplates and combs. But I can hear, acoustic, a difference
between brass and phosphor bronze. I think Seydel's steel reeds sound a lot
like phosphor bronze, though they have a little stronger sound.
You can argue this stuff ad infinitum/nauseum... tube versus solid state,
analog versus digital, solid cabinet versus ply or mdf, 1/2" versus 5/8"
baffles, different kinds of mics, different kinds of pickups on guitar,
even one brand of cable over another, or the urethane versus lacquer
coating on a guitar, or the material that your guitar pick is made of. All
of this stuff is debated and I've read countless arguments on every side of
all of these. I suppose everything affects tone in some way, but I tend to
pay attention to the most immediate factors, at least as I judge them. But
I think I realize that the audience could care less and doesn't discern the
difference between a $125 Fender Squier and a $4000 Custom Shop job. Only a
musician who is really really in it all the time can hear and discern any
difference.