Rototom

The Rototom is a drum developed by Al Payson, Robert Grass, and Michael Colgrass that has no shell and is tuned by rotating. A rototom consists of a single head in a die-cast zinc or aluminum frame. Unlike most other drums, this type has a variable definite pitch. Composers are known to write for them as tuned instruments, demanding specific pitches. Rototoms are often used to extend the tom range of a standard drum kit. They were commercialized by the drumhead company Remo Inc., of North Hollywood, California.
Drums and drumheads.
Tuning.
Rototoms can be tuned quickly by rotating the drumhead, which sits in a threaded metal ring. Rotation raises or lowers the tension hoop relative to the rim, which increases or decreases the pitch of the drum by increasing or decreasing the tension of the drumhead.
Sizes.
Remo currently markets Rototoms in seven sizes — 6" (15.2cm), 8" (20.3cm), 10" (25.4cm), 12" (30.5cm), 14" (35.6cm), 16" (40.6cm) and 18" (45.7cm) diameters, each tunable over an octave's range or more, although the company notes that “the practical range for fullness of sound is approximately a sixth interval.” Each size can produce various effects, depending upon the drum head and its tuning.
Drumheads.
Rototoms are furnished with ""Controlled Sound" Black Dot" drumheads as standard, where the reinforced black central sound area is said to provide ”compactness of sound with minimum ‘overring’ plus great durability.” Other heads, each of which may offer distinctive tonal differences, are also available, including "Pinstripe," which offers “a dampened tom-tom sound — wet, flat and funky”, "FiberSkyn," which produces “a round, dark tom-tom sound...especially suited for recording use and in tuned tom-toms for general orchestral use, and "Timpani," intended for “purity of sound and consistent performance.”
Applications.
Rototoms can replace more specialized drums and, when equipped with timpani drumheads, replicate the timpani's range and timbre but with a distinctive tone. Jazz, rock and studio performers use Rototoms both as a solo voice and as conventional tom-toms; they can be rapidly tuned to produce glissando effects and can be arrayed for a virtual percussion keyboard. For concert and marching band programs, Rototoms combine rapid tuning with portability and sound quality, working both as concert tom-toms and as practice timpani. For stage bands and jazz ensembles, drum kits are fitted out with batter heads. When tuned to the mid-range, they have an indefinite pitch with fewer harmonic overtones than conventional tom-toms; tuned to the high range, they produce a latin percussion sound instead. 
Rototoms can assist students in ear training and in developing their timpani techniques and — because of their portability, storability and relatively low cost — are often used by professional performers as practice instruments. They are also used as definite-pitched instruments in elementary music programs, such as Orff Schulwerk, where their sound quality, pitch stability and rapid tuning are assets.
Musical repertoire.
Published percussion solo and ensemble literature calling for ”tuned drums” or “small tom-toms” may be appropriately performed on Rototoms, and some composers, such as William Kraft and Michael Colgrass, have written works specifically for Rototoms.
Notable users.
Famous drummers who used rototoms include Bill Bruford (of Yes, King Crimson and U.K.) and Terry Bozzio (of Frank Zappa's band and the U.K. band).