If a navy blue suit and a navy satin necktie are the lounge suit's version of formality for the evening, and I for one think they are, then the dark gray suit and black satin necktie are the equivalent for day wear.
Formal day wear of course combines a black jacket with patterned gray trousers but few men own that any longer. Still, serious occasions do arise from time to time and require something to wear. Here is where the justly-maligned-for-evening black satin four in hand finds its place with a gray suit, black shoes, a white pocket handkerchief and a white shirt. Continue to wear your matte grenadine to funerals but wear black satin to sit for your portrait.
-Photo: Richard Avedon