Cris Forster's 'Just' Musical Menagerie

Jeff Kaliss on July 23, 2013

On Sunday mornings, Cris Forster, with his wife Heidi, takes a break from the making of music to roam the flanks of Mount Tamalpais. Up on that mountain, and down at his Chrysalis New Music Studio in San Francisco, he finds the thrill of discovery to be much the same.

“I continuously see things I’ve never seen before, and I’ve been hiking there now for forty years,” says the 65-year-old Forster about his weekly outings. “I’ve learned to observe, to hear things I’ve never heard before, to not pass judgment, and to suspend questions until they are answered. The whole process of pursuing the unknown goes everywhere.”

Forster’s pursuit of musical unknowns has involved the authoring of an Olympian 926-page treatise, Musical Mathematics: On the Art and Science of Acoustic Instruments (Chronicle Books, 2010), and the creation of seven, sizeable, one-of-a-kind instruments of his own, now housed in his South of Market studio, a short drive from his and Heidi’s Potrero Hill homestead.

His quest dates back to the mid-1970’s, just after he’d completed two college degrees, the first in history (from UC Santa Cruz) and the second in piano performance (from San Francisco’s Lone Mountain College). He’d been supporting his studies by working as both a piano teacher and tuner.

Tuning and working within the instruments sensitized Forster to both the mathematics and the mechanics of securing the 12-tone scale within which Western classical music has evolved for the past four centuries or so. “Various civilizations use prime numbers [integers divisible only by themselves and 1],” Forster points out about the formation of scales, “but we really don’t progress beyond prime number five.

Listen To The Music

Heidi Forster and Chrysalis Foundation interns perform Cris Forster's "Blue Nights," in 2005.

So I was seduced into wanting to know more about why those numbers existed as they did, about the history, and even the etymology, of the numbers. So one morning in 1975, I put an ad for my 1927 Chickering in the paper, drove down to San Jose in a U-Haul truck, and bought a bandsaw. I sold my piano to buy a bandsaw, and I’ve never looked back.”

Forster credits an eighth-grade shop class at Lincoln Junior High in Santa Monica with preparing him to deploy the latter device as well as he had the former. “I had huge tables of [musical] ratios that I knew existed, in a historical context. But in 1975, there were no computers, so the best way to make those things audible was to build an ancient six-stringed instrument which the Greeks called a ‘canon.’ With it, I found locations on the strings of intervals I’d never heard. And I was gone. What transformed me was, I was no longer able to classify all intervals into two camps, consonant or dissonant. And I have never listened the same since.”

“I put an ad for my 1927 Chickering in the paper, drove down to San Jose in a U-Haul truck, and bought a bandsaw. I sold my piano to buy a bandsaw, and I’ve never looked back.” - Cris Forster

Some 20th-century musicians have explored the virtues of “just intonation,” a mode of tuning which stands as an alternative to the “equal-tempered” 12-tone scale. Equal temperament, promoted in the title of J.S. Bach’s 1722 composition for keyboard The Well-Tempered Clavier, involves small compromises of tuning intended to facilitate transposition and modulation between keys. Champions of just intonation, on the other hand, strive for pure intervals and harmonies, based on the “natural” harmonic series of simple mathematical ratios. So accepted is equal temperament in the West, that the effects of just intonation and any alternative tuning system are considered aberrant by most musicians and listeners.

Forster furthered his study of mathematics and physics with David Canright, a professor at the Naval Postgraduate School in Monterey, and contacted such like musical minds as post-minimalist composer Peter Garland. From 1976 to 1980, Forster functioned as curator and archivist for the Harry Partch Foundation. At the same time, he began designing and constructing his own large-scale instruments, all tuned in accordance with the principles of just intonation.

“When you buy an instrument in the store, you’re also buying the [standard] scale, which is built into the instrument, and the timbre, which is associated with that instrument,” Forster points out. “For most people, those are constants. For me, those two are variables. When I build, the real impetus is to hear new scales and experience new timbres.”

A Workshop Tour

After successfully eliciting these from his Little Canon, Forster enlarged his endeavor with the Chrysalis, for which both his later studio and foundation were named. “This is basically a circular harp,” he says, pausing beside the graceful and fantastic-looking Chrysalis as we tour the studio.

“It’s very unusual, because it has two facing soundboards, and I don’t know of any other instrument in this world that has that. Eighty-two strings on the right soundboard, 82 on the left, with an air chamber in the middle.” The height from the floor to the top of the two wheels is almost five feet. “You can play it stationary, or you can spin it. It’s an unusual instrument, so it would not lend itself at all to traditional harp or guitar music.”

He moves on to the Harmonic/Melodic and a Bass Canon, much larger (48 and 72 strings, respectively) than Forster’s earlier version. The strings for the Bass Canon were fabricated on a string-winding machine made by Forster, “because the kind of strings I needed, I cannot buy commercially. In order for a string to produce the harmonic series without too much distortion, it needs to be thin and flexible. The shorter and thicker a string [like those used commercially], the more inharmonicity.” The multiple bridges on both canons are infinitely adjustable, as are the pitches produced by the strings.

“We don’t have to be programmed to speak only one language, or to have one set of values. And the idea that our learning about these things is terminated at the age of six or eight, I find extremely offensive.” - Cris Forster

Nearby stands a pair of rather different marimbas. The smaller Diamond Marimba is based on a chordal scale laid out by an earlier visionary, Max. F. Meyer, a psychologist who, in 1929, published The Musician’s Arithmetic. There are tone bars which produce microtones, pitches between the standard semitones.

The bars of the 12-foot-long Bass Marimba are traditionally aligned, along a single axis, but cover a much wider range and extend much lower in pitch than a concert marimba, down to 49 cycles per second. The design of the instrument required Forster to fashion both cavity resonators and traditional tube resonators, and to learn how to tune both the resonators and the Honduras rosewood bars, matching the upper harmonics with the fundamentals.

David Canright, Heidi Forster, and Cris Forster

Heidi steps up to demonstrate the fascinating Glassdance. It bears a passing resemblance to Benjamin Franklin’s treadle-operated glass harmonica, but has a direct current motor turning a set of 48 brandy snifters, which Forster tuned by slicing off rings of glass with diamond tools. “When I first heard it,” in 1983, “I fell in love with it,” Heidi recalls. She dons a special pair of leather gloves and dips her fingers in alcohol, allowing her to elicit quick, steady, angelic tones from the rotating snifters.

Most familiar to a visitor, and more easily playable, is a modified upright piano, positioned next to the Glassdance. But this is a far cry from your ordinary Kawai. To effect the just intonation implied by his name for the instrument — Just Keys — Forster had to remove the factory-installed strings and go through three attempts at installing his own home-wound strings, before he was satisfied. He then color-coded the keys as sets of multiples of prime numbers, and labeled both the Just Keys and the other instruments with numerical ratios representing the relationships of the pitches (5/4 for a major third, 2/1 for an octave, and so forth).

The labeling is not so much for the players as for himself, as the primary composer (so far) for all his instruments. “It helps me to understand and learn more about where I am,” Forster explains. “All these ratios have identities for me, in the same way that somebody else would identify with F-sharp or A-flat. I don’t use letters, I use numbers, but the identities are exactly the same.”

United by a Mission

Just Keys Will Gullette

Mid-way through the creation of his musical world, Forster established the nonprofit Chrysalis Foundation, in 1982. “We are devoted to the idea that the future of music depends on the integration of timbres and tunings as raw ingredients in an expanding, flexible, and highly nuanced tonal palette,” reads the mission statement on the Chrysalis Foundation website. “By recognizing the art of tuning as a variable rather than a constant, music can once again become a vital force capable of expressing and addressing the complexities of our modern minds and spirits.”

Heidi, who had originally met Cris when she was a San Francisco Conservatory piano student dorming at Lone Mountain, married him in 1985, and functions as the Foundation’s president. Their nonprofit status has facilitated funding of Forster’s work, as well as the donation of what would have been costly materials (including the brandy snifters).

The Foundation also sponsors internship programs which have attracted several dozen music students, some from the Conservatory, in 2005 and 2012, with financial backing from the Argosy Foundation Contemporary Music Fund and (in 2012) the San Francisco Arts Commission. The interns studied with Forster, acquiring facility on the unfamiliar instruments and learning their diverse forms of notation. In 2005, as the Chrysalis Ensemble, the interns and their teacher presented a public premiere at the studio of Forster’s Blue Nights, for Glassdance, Just Keys, Bass Marimba, and Bass Canon.

Other ensemble pieces were showcased at the interns’ 2012 concert, some of which are featured on a DVD titled A Voyage in Music (available at the Foundation website), which also includes interviews with the Forsters and with some of the students, testifying to their improved awareness of and sensitivity to timbre and pitch.

Beyond Tuning Conventions, the Book

The preparation and publication of the nearly-thousand-page Musical Mathematics took at least a decade, “until I finally had to force myself to stop,” says Forster. The scholarship behind his meticulously documented study of the physical and mathematical properties of strings, bars, resonators, and varieties of tunings throughout history and around the globe, took a lot longer, of course. The book includes examples from his compositions, descriptions and specifications of his original instruments, and complete instructions on building your own Little Canon. Characteristically, Forster designed, illustrated, and typeset the tome himself; his wife edited it.

The author’s extension beyond contemporary Western conventions is as impressive as his inquiry into the fundamentals of musical sound. “The subject of musical mathematics is literally as universal a language as music is,” he maintains.

“But I wasn’t trying to be universal. I needed to know why, to us trained in Western music, what clearly sounds like a dissonance — especially in Arabian and Persian music — is clearly a consonance in other civilizations. We don’t have to be programmed to speak only one language, or to have one set of values with respect to good or bad, positive or negative, consonant or dissonant. And the idea that our learning about these things is terminated at the age of six or eight, I find extremely offensive.”

To refer to his approach to integrating his acoustic discoveries, "I actually coined a word, 'ambisonance'," for sounds that are "neither consonant nor dissonant but needing a musical context to give them one or the other inclination."

Listen To The Music

Cris Forster performs his setting of Walt Whitman's "A child said, What is the grass?", accompanying his vocals on the Chrysalis, in 1986.

Musical Mathematics now occupies a greater-than-average space on the shelves of 130 libraries world-wide, including those at a half-dozen University of California campuses, Stanford, Harvard, Yale, Juilliard, and universities in Zurich, Singapore, and Sydney. (The San Francisco Public Library has a couple of copies, one of them circulating.) “I do have seven wonderful reviews of the book,” Forster reports.

But despite its manifest value to historians, mathematicians, musicologists, music theorists, and instrument-makers, “I haven’t heard one word in three years from anybody in institutions of higher learning, about anything. Not an e-mail, not a grunt. I don’t know whether it’s a phobia, a hatred, an unbelievable close-mindedness and arrogance, even hubris, against numbers. I don’t understand it at all.”

Undeterred, Forster continues to compose and to plan for a third session of internships in 2014. He’ll be posting high-quality video of last year’s performances to YouTube, planning recordings, and hoping to soon present one of his large ensemble works, Ellis Island/Angel Island: A Vision of the American Immigrants, in a large public venue outside his studio, accommodating a troupe of dancers and bigger audiences.

The Forsters will also keep climbing upwards towards their weekly perspective from the verdant heights of Marin County. “You develop an appetite for experiencing things that are literally awesome,” Cris sighs.

[The writer appreciates the role of Nancy Quinn and Tom Driscoll, who introduced him to Heidi Forster and the work of Cris Forster.]

Did you enjoy the article?

Sign up to our weekly newsletter to receive the latest articles every Tuesday