It's an interesting question, Rami - and probably very complicated.
Certainly in the world of acoustic guitars, violins, etc., there are quite a few people that will insist the finish makes a difference, and I'm strongly inclined to agree. However, I'll go out on a limb here and assume that your question pertains to the finish on a solid body Alembic (and a bass, for that matter).
Let's assume the finish (or paint, as Mica prefers) is identical, and the question is whether it ends up satin or gloss. Now, we know that Alembic will make a gloss instrument with a satin neck, so how do the do that? It could be either (a) they buff everything out to gloss, and then rough up the neck a bit, or (b) they sand everything to an even level, say 1000 grit or so, but then only buff the body and not the neck.
I really don't know what they do (and am curious). But it seems like (b) would be less work, so let's assume that for a moment. In this case, the finish on the glossy part would end up slightly thinner than the satin, because it's taken down more. In general, you could stop at satin, or proceed to make it glossy, and the glossy finish should end up thinner - which seems like it would be less of a seal, in terms of breathing.
However, a reliable source (experimental physicist) has explained to me on several occasions (usually while we're refinishing the bottom of his sailboat...) that at the microscopic level, there is an important difference between sanding and polishing. If you think of the surface as a bunch of sharp mountains and valleys, sanding mostly cuts off the tops of the mountains. In contrast, polishing is more like a bulldozer, pushing the tips of the mountains down to fill in the valleys.
So if you buy that, then a gloss finish could actually provide more of a seal, even if it is marginally thinner than stopping while it's satin. But putting aside the obscure theory, in reality Alembic seems to put on so many coats of finish that I seriously doubt there is a difference in seal between a satin and gloss finish.
So what do we mean by seal? Certainly, even a gloss finish does not provide a complete moisture/vapor barrier - over time, the woods will dry out, and you can see this in the differential shrinkage that occurs, e.g. between the maple and ebony neck lams.
But that may be a long term effect, and in terms of tonal characterstics, the question is more whether extremely short term vibrations of the wood, can express themselves (bleed through) the finish. And if so, would it be enough to really affect the tone?
I'll put a stake in the ground here. My best guess is that if you had two identical instruments, one entirely satin and one gloss, you would not be able to hear the difference. I'm assuming here that the finish is sufficiently thick that the mountain/valley thing doesn't matter.
The more interesting case to me is whether an oil finish would sound different. Here I think the answer is maybe. The usual finish is essentially adding a coat of plastic, which you might think of as almost an extra laminate or something. It seems likely that it will somehow affect the resonance, perhaps by increasing reflections within the body, for certain frequencies, or something (I'm just making this up, of course). If there is some effect here, I doubt it matters whether it is satin or gloss, only whether you have that extra coating.
True, an oil finish (such as tung oil) should help fill and stabilize the surface of the wood, but much less so than the usual stuff, and clearly it will allow the wood to dry out more quickly (breathe) if not properly maintained.
So I don't know what it means, it's just an interesting question to me, and fun to think about. My personal opinion/best guess is that if you're going to put the usual finish, on a solid body Alembic bass, then you probably won't be able to tell whether it's satin or gloss, except by feel.
That may also be the case, comparing oil or gloss (I think it's some sort of polyester, but I'm too lazy to look that up right now).
For me personally, what matters here is that with oil, the wood just feels more alive and natural to me, and I think that as a result I interact with it differently. As to whether the wood is actually breathing, in time with the music, I really can't say.
-Bob
[edited to add the following]
Took me too long, and I think I like Mike/jlpicard's answer better - short and to the point.
As Mike says, I think it matters much more in the case of an acoustic instrument, and it's probably less a case of breathing, and more a matter of inhibiting motion.
Even so, I'm still inclined to believe that finish can make a tonal difference on a solid bodied instrument, assuming it's thick enough. But I doubt it matters whether it's satin or gloss.
(Message edited by bob on March 26, 2006)
