Another hat worn by Bob Walters, in addition to orchestrator and conductor, was adding the percussion instruments of Mark Tree and Orchestra Bells to some of the numbers.
At different times Mr. Walters brought those percussion instruments to the Bias studio and played those instruments to add them to the recordings.
For details about Bob Walters, for easy click reference, you can see his bio at: Bob Walters.
A Mark tree (also known as a chime tree or set of bar chimes) is a percussion instrument used primarily for musical color. It consists of many small chimes – typically cylinders of solid aluminium or hollow brass tubing 3/8" in diameter – of varying lengths mounted hanging from a bar. The chimes are played by sweeping a finger or stick through the length of the hanging chimes, or the strings that suspend the chimes. They are mounted in pitch order to produce rising or falling glissandos.
Unlike tubular bells, another form of chime, the chimes on a Mark tree do not produce a definite pitch. They produce inharmonic (rather than harmonic) spectra.
The Mark tree is named after its inventor, studio percussionist Mark Stevens. He devised the instrument in 1967. When he could not come up with a name, percussionist Emil Richards dubbed the instrument the Mark tree.
The Mark tree should not be confused with two similar instruments:
A percussion instrument consisting of a set of metal bars which are sounded by being struck with a hammer. Each bar produces a specific tone. The bars are arranged in the same manner as a piano keyboard, and thus the Orchestra bells are fully chromatic. The written range is from G3 to C6 and sounds two octaves higher than written.
The Bell lyre and Glockenspiel are versions of the Orchestra bells designed for marching.
Related modern instruments are the Tubophone, which uses a keyboard with tubes instead of bars, and the Vibraphone, which has resonating tubes beneath its bars that vibrate using electricity. See also Xylophone, a musical instrument having graduated wooden slabs that are struck by the player with small, hard mallets. The slabs are usually arranged like a keyboard, and the range varies from two to four octaves.