"Trumpets and violins I hear in the distance." Sorry, wrong genre.

The U. of Chicago Spanish-English dictionary says mariachis are "typical of Guadalajara", so I think you're right, Bill.

Mariachi music often strikes me as rather silly, based as much on sound effects as on music, but I can still enjoy it when it's well done.

The big guitar is called a guitarrón. (Let's see how that comes out!) I've heard of a bajo sexto ("low sixth"), which I think is about the same thing. I suspect the name of the twelve-string guitar would be doble sexto or sexto doble ("double sixth"). And like Mark, I've only seen/heard them play chords. However, I wouldn't call that being used as drums. I'm told, incidentally, that a lot of mariachis are starting to use brass instead of guitars for the bass parts nowadays, but the north-of-the-border ones I've heard here in New Mexico don't have tubas. I haven't seen a mariachi band with an accordion, but I've only seen a few.

Yes, lots of strong, almost operatic tenor voices. The last one I heard (Mariachi Porvenir, from Santa Fe) had a powerful contralto lead singer--an interesting difference.

Phil, I'm not too sure about the different genres, though I can sometimes tell them if I hear them. "Tejano" is just Spanish for "Texan". I think it would sound a lot like U.S. country music with an accordion, but that's also my definition of "Tex-Mex" and "norte&tilden;o". (Tex-Mex may have more of that plaintive sentimental stuff, e.g., "Before the Next Teardrop Falls", by Freddie Fender.)

"Ranchero" is music from rural Mexico--very simple harmonies (unlike the sophistication of mariachi music) and folk or folk-like melodies with those two long notes at the end of the phrase. I think much of it's from the 1900-1950 period. Can't have a fiesta without it. Cormac McCarthy says that when you hear your first ranchera (a ranchero song), you know all there is to know about Mexico. When you hear your hundredth, you realize you know nothing.