There used to be marching tympani, however when corps started becoming more concerned with better sound quality and symphonic techniques, the use of marching tymps ended. I believe it was sometime around the late 70's-early 80's.
The marching tymps were made out of fiberglass and didn't sound very good.
I know of some parade groups that march bells, but generally the pit equipment gets left behind. The Marine Corps Drum and Bugle Corps usually has a guy that marches out with a 3 octave xylo or marimba, but he parks near the front sideline for most, if not all of the show.
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The Cavaliers - Baritone 1993
Hawthorne Caballeros - Baritone 1988, Contra 1989-1995, Bass 6/5 1996-1998
Pequannock HS - Marching Instructor 1995
Saddle Brook HS - Percussion Instructor 1995
Lodi HS - Percussion Instructor 1996-2003