What type of mute uses the rubber end of a plunger to create sound modulation?

The type of mute that uses the rubber end of a plunger to create sound modulation is the plunger and hat mute. This mute is particularly associated with brass instruments, especially the trombone and trumpet. The plunger allows musicians to create a variety of expressive sounds—such as a 'wah-wah' effect—by moving the mute in and out from the bell of the instrument.

This technique gives the performer a versatile tool to achieve different tonal colors and dynamics, as the rubber end provides a soft edge to the sound while also allowing for nuanced control over the modulation of pitch and volume. The cap-like shape of the mute can also be used on its own to create a muted quality without the sliding effect produced by the rubber side.

In contrast, other types of mutes serve different purposes: a bucket mute softens the sound without significant tonal alteration, a straight mute gives a more focused and bright sound, and a cup mute, while also designed to soften sound, does so in a way that maintains more traditional tonal qualities. Each mute contributes uniquely to the musician's palette, but the plunger and hat mute stands out for its ability to create those distinctive modulations.