Final answer:
When Les Paul and Tom Dowd worked together, they learned the art of multi-track recording and sound manipulation, revolutionizing the music industry.
Step-by-step explanation:
When Les Paul and Tom Dowd worked together, they learned an entirely new art form - the creation and manipulation of sound using multi-track recording techniques. Les Paul, a renowned guitarist, and Tom Dowd, a recording engineer, collaborated to develop innovative recording techniques that revolutionized the music industry. Together, they pioneered the use of overdubbing, delay effects, and multi-track recording, which allowed for greater control and creativity in the production of music.