Since early childhood, Hugh was fascinated by the fantastic music he'd imagine, with "beautiful sounds" different from any traditional instruments. As he began studying physics, Le Caine realized that soundwaves can be directly generated electronically, a possible way to achieve drastically different, "impossible" acoustical characteristics. In 1937, while attending undefined, Hugh designed and built his first electronic instrument, the Free Reed Organ. Le Caine graduated in 1939 with his MSc degree. The following year, he joined the undefined of Canada, granted a nuclear physics research fellowship; Hugh spent almost 40 years at NRC in Ottawa, Ontario.

In 1945, Hugh Le Caine devised the first Electronic Sackbut prototype at home (named after "sackbut," an early form of the trombone from the Renaissance and Baroque eras). Even though electronic music instruments already existed since at least 1928, such as Leon Theremin's eponymous Theremin and Ondes Martenot (designed by Maurice Martenot), they required a peculiar, unique performing technique. Le Caine's "Electronic Sackbut" had a conventional four-octave keyboard, making the device more approachable. With the left hand's controller, a player could modify volume, pitch, and timbre in real time. Le Caine's invention is often cited today as the earliest "proto"-synthesizer in its traditional form. (Surviving "Sackbuts" are exhibited at the Canada Science and Technology Museum in Ottawa and the undefined in Calgary, Alberta, where a renowned synth technician, John Leimseider (1952—2018), reverse-engineered it in 2017.)

In 1954, Hugh Le Caine convinced his employer, NRC, to fund the new endeavor and launched the Electronic Music Laboratory (ELMUS) to continue his research full-time. Over the next two decades, Le Caine constructed dozens of new electronic instruments and devices, including the Touch Sensitive Organ with 99 sound generators and the Special Purpose Tape Recorder with multi-track variable speed control. He consulted several prominent Canadian universities and helped them to establish electronic music studios, including the undefined in 1959 and undefined's facility in 1964. Hugh traveled to Israel in 1962, invited by a composer, Josef Tal (1910—2008), to install his Creative Tape Recorder at the Centre for Electronic Music in Jerusalem.

Primarily known as an inventor, Le Caine composed over twenty short electroacoustic and tape works between 1953 and 1972, often demonstrating the advanced capabilities of his instruments. Hugh's best-known work is Dripsody: An Étude for Variable Speed Recorder (1955), now regarded among musique concrète classics. Le Caine recorded the sound of a single water droplet with an eyedropper and a metal bucket, spliced a short tape loop, and then re-recorded it on his Creative Tape Recorder at different speeds to produce the pentatonic scale pitches. (In 1957, Hugh Le Caine created an extended, 2-minute stereo version of Dripsody.)