Philadelphia's history as a driving force for technological advancement stretches back centuries, having served as the home for countless inventors since before the nation's founding. The kickoff date for Philly Tech Week marks the 85th anniversary of one of the city's major technological milestones, which involved close collaboration between Bell Labs and the Philadelphia Orchestra.

On April 27, 1933, music enthusiasts gathered at Constitution Hall in Washington for a special performance. The event featured the Philadelphia Orchestra, then conducted by the legendary Leopold Stokowski. Instead of rows of world-class musicians arranged on stage, however, the audience sat before cutting-edge loudspeakers designed and built by Bell Labs (the research and development branch of the American Telephone & Telegraph Co., or AT&T). The Philadelphia Orchestra remained in its home city, stationed in front of special microphones (also designed by Bell) arrayed inside the Academy of Music. The audience experienced two feats of technological magic that evening: the first live transmission of a concert through a telephone wire and the first public showcase of stereophonic audio.

Example of loudspeaker installed for radio transmission from Philadelphia to Washington, D. C., photograph by Bell Telephone Laboratories, Inc. (1933).
Historical Society of Pennsylvania
Example of loudspeaker installed for radio transmission from Philadelphia to Washington, D. C., photograph by Bell Telephone Laboratories, Inc. (1933).

Each partner in this groundbreaking project contributed enormously to its success. Stokowski was both a master-class artist and an advocate for integrating technology into music. Beginning his widely celebrated tenure with the Philadelphia Orchestra in 1912, Stokowski led the keystone Philadelphia cultural institution on to a number of artistic triumphs and technological firsts throughout his 29-year career. In 1925, the Philadelphia Orchestra recorded "Danse macabre, Opus 40," by the French composer Camille Saint-Saëns, which resulted in the first orchestral work recorded using the electrical recording process. By 1929, Stokowski and his world-renowned orchestra had performed the United States' first-ever commercial radio broadcasts of a live symphony, disseminated to the entire nation by NBC.

These early broadcasts propelled Stokowski to find even better technological solutions for the orchestra's modern-age experiments. Frustrated at what he considered the inadequate sound quality of the NBC broadcasts, Stokowski turned to Bell Labs for ideas to take his ambitions for the Philadelphia Orchestra to the next level. Bell had long worked on improving the quality of transmitted and recorded sound, primarily in the service of further developing telephone technology. Dr. Harvey Fletcher — a University of Chicago-trained physicist — served as Bell's director of acoustical research in the early 1930. Under his guidance and in conjunction with the Philadelphia Orchestra, Bell produced a number of groundbreaking audio technology advancements during this period.
In 1931, Bell installed microphones capable of capturing previously unimaginable frequency ranges in the Academy of Music's basement with the intention of recording  the Philadelphia Orchestra. Stokowski kept the project a secret, withholding it from orchestra members as he and Bell produced experimental records, including the first-ever stereophonic record, which featured Maurice Ravel's arrangement of Modest Mussorgsky's "Pictures at an Exhibition" and Alexander Scriabin's "Prometheus: The Poem of Fire."

Two years later, these collaborators made history yet again with the April 1933 concert. Associate conductor Alexander Smallens presided over the orchestra in Philadelphia, while Stokowski and Fletcher worked the machines receiving the transmission at Constitution Hall. This trailblazing production demonstrated the immersive experience of stereophonic sound and presaged stereophonic broadcast transmissions that would later reach mass audiences through radio.
The Inquirer described the event in grand terms: “For those alive and alert to the significance of the episode, it took rank as an epochal event in the history of musical performances.”

Together, Bell and the Philadelphia Orchestra contributed enormously to the revolution of recorded and transmitted sound, forever improving the listening experience of the record-buying and music-appreciating public while cementing Philadelphia's important role in the development of audio technology.

Patrick Glennon is a communications officer at the Historical Society of Pennsylvania.