A drum kit (or "drum set" or "trap set" - the latter almost a moribund term) is a collection of drums, cymbals and other percussion instruments arranged for convenient playing by a sole percussionist (drummer), usually for jazz, rock, or other types of contemporary music. Such a kit has been an integral part of most popular music since the jazz of the 1920s, until the arrival of synthesised and sequenced percussion (such as drum machines) replaced drums in some electronic music. Companies such as Simmons (in the 1980s), Yamaha, Roland and many others have created electronic drum-sets which use pads or triggers (mounted on acoustic drums) to play sampled or synthesized sounds. The trend in electronics since the late 1980s has been away from overtly electronic sounds and less towards an intensified acoustic sound.
Developed primarily in the United States, early drum kits were known as traps kits (possibly derived from contraption due to the piecemeal nature of early kits) and usually consisted of a bass drum, a snare drum on a stand, a small cymbal and other small percussion instruments mounted on the bass drum or a small table, all played with drum sticks or brushes except for the bass drum. The bass drum was sometimes kicked to produce a sound, and is occasionally still called a kick drum, though bass drums are now nearly always pedal-operated, and sometimes even played with two pedals to allow for greater speed. Trap set survives in the term trap case still given to a case used by a kit drummer (or any percussionist) to transport stands, pedals, sticks, and miscellaneous percussion instruments other than drums and cymbals.
The exact collection of components to a drum kit varies greatly according to musical style, personal preference, financial and transportation resources of the drummer. At a minimum a kit usually contains a bass drum sitting on the floor and played with a pedal, a snare drum on a stand, two or three tom-toms, some of which are mounted on top of the bass drum and the largest typically free-standing alongside it (on the floor - hence the word "floor tom"), a hi-hat (two small cymbals played by means of pedal) played with the left foot, a ride cymbal and a crash cymbal arranged on stands on the right and left. The drummer sits with the snare drum between his legs, his left foot on the hi-hat pedal and his right on the bass pedal. He will usually play with sticks, but may also use brushes, mallets, hands, or any of a variety of "multi-rod" sticks.
Some drummers may add a second bass drum (played by the left foot), additional toms, more cymbals, tambourines, woodblocks, cowbells, electronic pads that trigger sampled sounds, or any of a whole galaxy of accessory instruments. Some drummers, such as Neil Peart and Terry Bozzio, have gone to extreme lengths and built massive kits including features such as ranges of tuned tom-toms, allowing them to contribute melodically as well as rhythmically. These huge kits reached their zenith in the arena rock of the 1970s, and the trend since then has been towards a smaller instrument.