Drum module

An electronic drum module is an electronic or digital music device in an electronic drum kit that serves as the central processing unit and sound module. The drum module creates or produces the drum kit sounds or other sounds selected by the drummer. By itself, a drum module cannot play or sound drum beats. It only produces drum sounds when a performer strikes electronic drum pads or acoustic drum kit instruments that have electronic "triggers" (or sensors) attached to them. When the electronic drum pads or trigger-equipped instruments are struck, this sends a signal to the drum module, which produces the corresponding electronic drum sound (or other sound). Even when drum pads and/or triggers are connected to a drum module, the drum module by itself does not make any audible sound. Like other electronic instruments such as the synthesizer, the drum module only outputs an electronic signal. The performer can hear this signal by connecting headphones to the drum module (i.e., for individual practice) or by plugging the drum module into a amplifier and loudspeaker or PA system for audible practice or live performances. The drum module's output signal can also be patched into an audio console for concerts or sound recording. The nomenclature varies (see below). For example, electronic drum modules are called "percussion sound modules" in the case of Roland Corporation, or sometimes simply modules. A common colloquial term for this device is drum brain. (see below).

Electronic drum modules are included with most complete electronic drum kits (which include a drum module and a set of drum pads). Electronic drum modules can also be purchased as stand-alone units. In this case, the performer must also purchase drum pads and/or triggers which she can attach to regular acoustic drums. An electronic drum module is a special-purpose electronic device which accepts input from the drummer via external triggers that are hit with regular drum sticks. With an electronic drum kit, the player hits triggering devices as a synthesizer player would strike the keys of the synthesizer keyboard. Triggers may be pads or cymbal-shaped devices or piezo-electric pick-ups similar in function to a guitar pick-up. When the triggers are struck or activated by the vibration of a drum or other instrument, the electronic drum module interprets the signal and outputs the specific voice assigned to that trigger. The sound (or "voice") may be a sample or synthesized reproduction of any of a wide variety of drum, cymbal, percussion or other instruments, or even vocal sounds. It is similar in concept to modern MIDI musical keyboard workstations or synthesizers especially in that any sound available within a given module can be assigned to any trigger plugged into the module.

...
Wikipedia