 Photo by Will Gullette |
| Wild Flower Music by Cris Forster Cris Forster, Diamond Marimba Benjamin Koscielak, Bass Marimba |
| The Harbor Music by Cris Forster Heidi Forster, Glassdance Jacob Richards, Diamond Marimba Benjamin Koscielak, Bass Marimba |
| Dream Time Music by Cris Forster Jacob Richards, Diamond Marimba |
| Built: | 1989, San Francisco, California. | |
| Modified: | San Francisco, California. • 2008. Resonator channels. • 2010. Black anodized aluminum bar brackets, Delrin blocks, and Scünci cords. | |
| Dimensions: | Total number of bars: 54. Longest bar length: 16¾ in. Shortest bar length: 7.0 in. Height to first row: 34.0 in. Height to last row: 40½ in. | |
| Materials: | Honduras rosewood bars. Birch, teak, cast acrylic, Delrin, aluminum, brass, and stainless steel. HR-23 foam supports. | |
| Range: | From G3 (1/1) 196.0 cps to Eb7 (13/8) 2548.0 cps. | |
| Tuning: | Just Intonation. |
The Diamond Marimba has fourteen rows of rosewood bars mounted on a terraced platform. Beginning with the second row, each succeeding row rises a half inch above the previous row, so that the difference in height between the first and the last row equals 6½ in. Each bar is equipped with a tuned acrylic tube resonator that amplifies the frequency of the bar.
The marimba’s central section consists of a diamond-shaped lattice that includes seven ascending and seven descending diagonals of bars. Each diagonal includes seven bars. Diagonals that ascend from left to right sound major tonalities, and diagonals that descend from left to right sound minor tonalities.
From my book Musical Mathematics: On the Art and Science of Acoustic Instruments (see Musical Mathematics Pages > Table of Contents), below please find Figure 12.5, which illustrates the frequency ratios of Diamond Marimba I and Diamond Marimba II. The tunings of the fundamental frequencies of both Diamond Marimbas are identical. Regarding the tuning of the higher modes of vibration of bars, see Creative Aspects > Instrument Design Features.
(See also Musical Mathematics Pages > Meyer’s Diamond, > Partch’s Diamond, > Forster’s Diamond.)