Photo by Will Gullette





Blue Nights, by Cris Forster

David Boyden, Bass Canon
Heidi Forster, Glassdance
Isabelle Jotterand, Just Keys
Benjamin Koscielak, Bass Marimba




The Harbor, by Cris Forster

Heidi Forster, Glassdance
Jacob Richards, Diamond Marimba
Benjamin Koscielak, Bass Marimba




Lullaby, by Cris Forster
Heidi Forster, Glassdance






Built: ..... 1982–1983, San Diego, California.



1990, 2018, San Francisco, California.

Redesigned and remachined

modular drive transmission;

aluminum glass stems,

and stem components.

Dimensions: ..... Total number of glasses: 48.
Length of stand: 55˝ in.
Height of stand: 42˝ in.
Width of stand at wheels: 42.0 in.
Overall height of instrument: 76˝ in.
Materials: .....

Lead crystal glass, Douglas fir, birch, teak,

mahogany, E-A-R isodamp thermoplastic,

aluminum, brass, and steel.

Range: ..... Lowest glass: G above middle C.
Highest glass: Third G above middle C.
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 Benjamin Franklin’s glass armonica 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 motor 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.