This article is from the Drum corps FAQ, by Cathy Doser cathyd@halcyon.com with numerous contributions by others.
Rule 4.1.1: "All acoustic percussion membrane and keyboard
instruments (those not needing electricity to generate sound) are legal."
Rule 4.1.2: "Percussion keyboard instruments may use resonators.
A self-contained motor that is battery-powered is permitted to be used
on vibraphones only. This motor is not to be used for amplification,
but rather to produce a vibrato effect by turning the resonator
propellers. Electric amplification is not allowed."
 
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