Last year, I wore button up + tie most of the days, and I think a polo for one or two of the days, black slacks in either case.

Each day I didn't change during the day and didn't feel out of place. Ymmv.

Yes, one outfit for rehearsals (business casual is what I used) and another for Mass (formal: suit and tie for me) is a very practical consideration for colloquium attire. The suggestion made above about having more than one change of each is highly recommended unless you plan on doing laundry while you're there. If you can swing it, they have some fun with dress, such as White Suit Wednesday and Bow Tie Friday. These have come to me from Mr. Ben Yanke, so I would ask him for more details.

As admirable as I think the Meloche/Yanke suggestions are, I've noticed over the years that it seems (as I don't want to speak for them) both Turkington and Mahrt basically stayed with one or two sport coats (navy seems to be de rigeur) 2 pair of slacks (grey/tan), solid long sleeve shirts, and ties, all rotated in different combinations. Mahrt would do the day sans tie if the heat/humidity was high.
Warning on White Suit Day- MJM and I were the only two that celebrated that, and MJM changed for the evening. But he's such a fashionista.
And I recall that Tucker ranted on FB that oxford button collar shirts are inappropriate for men's formal wear. But he's pretty fussy.

And have a sign around my neck, "Can anyone point me to the Big Island Liturgical Congress? I gotta meet David Haas, stat!"

Just to give a straight answer to Carolus16's question, there aren't any real solid rules, but usually our chaplain Fr. Pasley makes an announcement in the first day or so urging the gentlemen to dress up a bit for Mass.

Matthewj has a porter employed for all his out-of-town trips, so I'd adjust expectations accordingly.

Matthewj has a porter employed for all his out-of-town trips, so I'd adjust expectations accordingly.

I thought I heard MJM refer to him as his man servant last year. Viva la revolucion!

And the women do not dress up....

G/Scelata wears the greatest hats!

Matthewj has a porter employed for all his out-of-town trips, so I'd adjust expectations accordingly.

The proper term is "valet": that's val-et, with the 'T' pronounced. cf. P.G. Wodehouse, J. Morse, et al.

Tucker is right -
Button-down shirts are not appropriate for either informal or formal attire. Informal = 'business' suit, formal = tuxedo, casual = sport coat or less. Button down shirts (Oxford cloth or other) are casual attire and may be worn with sport coats or no coats. Also, casual 'loafer'-styled shoes are not appropriate with informal or formal costume, only casual.

(The button-down collar is an American invention which originated in Ivy League realms as a way of keeping collars in place during sporting events.)

For my guys and boys in choir, I am glad they wear a shirt as opposed to a t-shirt. SO button down versus not is a non-starter.

Thanks, Charles. I was wondering what to wear.

Oh great, professor...now I don't know whether to sing Bernstein's "I feel pretty" or Purcell's "When I am laid."
At least I'll have the excuse of having been sequestered to the desert which once was the great San Joaquin during Colloquium. You know you've tried to kill me twice already, both of 'em during Vespers! ;-)

Well, Charles, I could say that that little loop was invented by a New England school marm as a means of snatching a lad who had put glue in her chair as he was trying to make his escape. But, that would be pure conjecture.

So, my educated guess, Charles, is that that little loop is for hanging the shirt on a hook or some such. If I ever find this in print I shall let you know. (And, you are spot on about those table place settings. It sort of depends on on which side of the pond one is - or whether one side of the pond is imitating the other. Or whether it's 'house rules'.)

There are a lot of sockless feet shod with Weejuns, boat shoes, and similar footwear in this sprawling and unlikely arts mecca. They generally seem to belong to persons who want to be seen as daring or unbound by rules, who can 'pull off' something that is a little bit uncouth but not reprehensible - sort of like those who wear tennis shoes with business suits. I find them quite amusing. Of course, one is supposed to pretend not to notice.

And, I remember well the rage for madras. I had a number of madras ties in various colours.

I'll wear what I wear and you'll like it.

I'll be decent, within the confines of my wardrobe. I was just feeling a little prickly at so many strong opinions.