Solid-body electric guitar: Paul designed the Gibson Les Paul and the SG electric guitar. 

Multi-track recording: Paul pioneered multi-track recording techniques, which began the modern era of audio recording.

Sound-on-sound recording: Paul introduced sound-on-sound recording, also known as overdubbing.

Echo chambers: Paul provided direction for the design of Capitol Records’ echo chambers, which are still used by today’s top recording artists. 

Harmonica holder: Paul invented an around-the-neck harmonica holder so he could play the guitar and harmonica without touching the harmonica.

Les Paulverizer: Paul designed the Les Paulverizer to demonstrate the sound-on-sound technique live.

Tape machine: Paul invented the first tape machine.

Digital delay: Paul invented digital delay.