Visible as the label "FREQ. ANL." on Belew's effects rack in Adrian Belew: Electronic Guitar at 2:36, with an explicit mention at 2:23. It was also used on Nine Inch Nails' The Downward Spiral, as mentioned in this April 1993 Guitar Player interview.

Adrian Belew: Electronic Guitar (1984)

I have several guitar synthesizers, a harmonizer and frequency analyzer, which is a sort of ring modulator...

Guitar Player, April 1993, "Adrian Belew & Trent Reznor: Nine Inch Nails Meets The Lone Rhino"

For his self-described "rambling" solos, Belew dusted off several vintage effects. "I used some sounds that I don't normally put on records for anybody else," he notes. "I also ended up climbing around in the back of my rack and connecting things together in ways I'd never done before. The two things they liked the most were the Foxxtone - an old '60s fuzz box - and an Electro-Harmonix Frequency Analyzer, an old version of a ring modulator. One of them suggested, What if you put those sounds together? So I did for the first time, and we got some really nice things."

Used on "Exithouse" and "The Rapture", as specified in this July 20, 2012 breakdown of a A Fine Pink Mist gear list printed in the October 1996 issue of Young Guitar.

Visible in this video and specified in its description.

An Electro Harmonix Frequency Analyzer can be seen on the floor of this live photo.

shown & mentioned in the video

Amongst the host of effects that Kaoru uses, the Dir En Grey website says he uses an EH-5000 by EHX.

In this 2007 concert review, a picture of Pace's pedalboard is visible. Another source is here. A pedal that we can see in his pedalboard is the EHX Frequency Analyzer.

In the Resident Advisor feature "Machine Love: Laurel Halo" by Ryan Keeling, Laurel Halo is shown using the Electro-Harmonix EH-5000 Frequency Analyzer V2, positioned to the right of her Boss Space Echo.

Masonna is associated with the Electro-Harmonix EH-5000 Frequency Analyzer V2, as it is listed among the gear used in the album Cosmos From Diode Ladder Filter by Space Machine, according to Discogs.

Jeremy Michael Ward is associated with the Electro-Harmonix EH-5000 Frequency Analyzer V2, as noted in his Discogs discography.

In a video uploaded by fukugangallery on YouTube, titled "2021.03.13『MACHINE HEADS』大野雅彦展　機材について," Masahiko Ohno's setup can be seen featuring the Electro-Harmonix EH-5000 Frequency Analyzer V2 at the 8:45 mark.

Ryuki Matsuno is seen using the Electro-Harmonix EH-5000 Frequency Analyzer V2 in a recent Instagram reel by matsuno_prompts, where he discusses his setup alongside the EH Nano BM, Digitech Whammy DT, and Line 6 HX.