I was amazed and amused to find this photo for sale on e-bay.
This is the clarinet section T-shirt. This must have been taken at Detroit Metro airport at the start of the trip. The Michigan Marching Band always dressed to impress on bowl game trips and these people are not in mid-70’s college student everyday attire.
The date on the back (pictured below) says December 26, which is exactly right.
So if you want it, visit historicimages-store on e-bay to see if it’s still available!