Undertone Audio is a high-end professional audio equipment manufacturer founded by producer/engineer Eric Valentine, longtime owner of Hollywood's Barefoot Recording studio. The company grew out of a custom recording console Valentine designed with engineer Larry Jasper after concluding that no existing console suited the way he wanted to track and mix records. That console's signal path became the basis for the gear Undertone now sells to other studios.

The lineup is built around discrete Class A circuitry and centers on the MPEQ-1 mic preamp/EQ/DI channel strip, the MPDI-4 four-channel mic preamp, and the UnFairchild 670M II, a modern reinterpretation of the Fairchild 670 vari-mu compressor. Other products include the UTEQ500 500-series parametric EQ (a port of the console EQ), the UNFa-1 compressor, the Pyra-Sum summing mixer, the Satellite Re-Amp, the GB Tracker, and the Vari-Cap. A separate digital division produces plug-in versions of the hardware, including a UnFairchild 670M mkII plug-in.

The brand is positioned toward mixing and mastering engineers and tracking studios that want hardware with vintage character and unusually wide control range. Reviews in publications like Tape Op and Mix highlight the EQ's flexibility and musicality, and Valentine's own production work — across rock, alternative, and pop records cut at Barefoot — serves as the most public demonstration of the gear.

Undertone Audio has 4 products cataloged on Equipboard, including Effects Processors and Preamps. Their gear is featured by 5 artists, with the strongest followings in Pop, Rock, and Folk, World, & Country. Notable users include Dave Clauss, Chris Chaney, and Ryan Petersen.