Recently while in Florence, Italy, for Pitti Uomo 94, I attended a Black Tie event at the Palazzo Corsini.
I wore a made to measure dinner suit from Tolley Savile Row here in Melbourne, Australia. The design I chose was single-breasted, large shawl lapels and plain pleated black trousers.
Now there are many die-hard rule followers when it comes to black tie and how a dinner suit/tuxedo should look and fit. Me, personally, not so much and I think this is where the personal style plays a massive part in individualising a look.
Traditionally a black tie suit was classed as a leisure suit. This doesn't mean that it wasn't formal, but it wasn't part of the military dress code; thus, it was for leisure and also ventless.
Military "suits" and jackets had a single vent as to be worn while riding a horse.
The suit style itself as the "rules" state can be single or double-breasted, shawl or peak grosgrain silk lapels, buttons, pockets and outer trouser seam, a cummerbund or vest, always a white band or wingtip collared shirt and black patent pumps.
Of course, nowadays there are slight variations to this dress code. Semi-spread collared stud-less or uncovered buttons, unpleated bibs, navy instead of black fabric, contrasting jackets, patent black oxfords or loafers and no vest or cummerbund.
Another change to modern-day black tie would be the adding of double vents to the jackets.
Due to body profiles changing, if one wore the traditional ventless jacket, they might look like a sack, or it would leave bunched up fabric at the small of the back.
This is due to more athletic builds (broader shoulders, small waists and prominent seats). So a double vent can taper the waistline, while still sitting clean over the seat.
So whether you have a black-tie event or are wearing one for a wedding, think about what you want out of a tuxedo or dinner suit and choose right for your body profile.