The Bass Marimba is by far the largest
and most powerful instrument Cris Forster has built. It is over
12 feet long, and all of the 24 exceptionally large bars are made
of Honduras rosewood.
This instrument has 19 standard wavelength resonators and 5 cavity
resonators. The reason for the cavity resonators is that extremely
low frequencies require extremely long tubes, which, in turn, would
require a high stand for the instrument and a high riser for the
musician to stand on.
In all 24 bars on the Bass Marimba, Cris tuned the first three modes
of vibration to produce exact harmonic ratios 1:4:8 in each bar.
Therefore, above the fundamental or first mode of vibration, the
second mode sounds the interval of the double-octave, frequency
ratio 4/1; and the third mode sounds the interval of the triple-octave,
frequency ratio 8/1. Cris developed this tuning technique because
in low-sounding bars the upper modes of vibration are clearly audible.
Despite its enormous size, this instrument requires only a screwdriver
to disassemble. Hand knobs hold all the large structural components
Started: 1983, San Diego, California.
Finished: 1985–1986, San Francisco, California.
Total number of bars: 24.
Longest bar length: 44.0 in.
Shortest bar length: 19 ½ in.
Length of stand: 145.0 in.
Height of stand: 40.0 in.
Width of stand at wheels: 44.0 in.
Height to bars: 36.0 in.
Honduras rosewood, birch, teak, mahogany, delrin, kydex, acrylic,
formica, aluminum, brass, and steel.
Lowest bar: Third G below middle C.
Highest bar: A below middle C.