 Photo by Will Gullette |
| Blue Nights Music by Cris Forster David Boyden, Bass Canon Heidi Forster, Glassdance Isabelle Jotterand, Just Keys Benjamin Koscielak, Bass Marimba |
| The Harbor Music by Cris Forster Heidi Forster, Glassdance Jacob Richards, Diamond Marimba Benjamin Koscielak, Bass Marimba |
| Lullaby Music by Cris Forster Heidi Forster, Glassdance |
| Built: | 1982–1983, San Diego, California. | |
| Modified: | San Francisco, California. • 1990. Yellow transmission chain. • 2018. Machined aluminum glass stems and customized mechanical fasteners. • 2024. New electrical components; customized Threaded Shaft Collars; newly invented Locknuts. | |
| Dimensions: | Total number of glasses: 48. Length of stand: 55½ in. Height of stand: 42½ in. Width of stand at wheels: 42.0 in. Overall height of instrument: 76½ in. | |
| Materials: | Lead crystal glass, Douglas fir, birch, teak, mahogany, E-A-R Isodamp thermoplastic, aluminum, brass, and stainless steel. | |
| Range: | From G4 (1/1) 392.0 cps to G6 (4/1) 1568.0 cps. | |
| Tuning: | Just Intonation. |
The Glassdance, which consists of 48 revolving tuned crystal glasses, belongs to a relatively rare family of friction instruments. It was inspired by an invention that Benjamin Franklin (1706–1790) called the glass armonica (1761) and is by far the most complex instrument I have built to date. In the detailed graphic, note that the machined aluminum stems of the glasses are mounted through the centers of red sprockets. A variable speed gearmotor coupled to a modular drive transmission rotates the glasses. Consequently, a performer may play two or more glasses simultaneously. This instrument has a remarkable sensitivity to touch, and a rich variety of tones and timbres.