Used on V.S.O.P., as specified in Herbie Hancock’s Electronic Instrument Glossary from September 14, 2016.

Phase Shifter – This is an effects unit that can alter sound using certain techniques to change the sound waves. While these effects units were originally large boxes with knobs and buttons, today they are most often small pedals used by guitar players. Herbie used the Country Man Phase Shifter on his 1976 album V.S.O.P.

A defective unit was used for the "end explosion" in the 1980 Doctor Who theme, as demonstrated in this excerpt of the February 2, 1982 episode of The Music Arcade at 5:22. An ARP Odyssey MKIII was run through it to produce the sound.

Tim Whitnall: Peter, what's this over here? It looks very old-fashioned to me.

Peter Howell: Well, it is rather, but it's a very useful little box. It's a phase unit that I used for the end explosion. Let's just turn it on. [Turns on the 968, which rings twice. Switches to the ARP Odyssey.] Let's get a sound out of this... That was the old sound we had... [Plays an explosion sound on the ARP Odyssey.] Well, that's a fairly normal explode that's coming out of there. If we put it through this box, we'll see that it's got a sort of fireworks sound with it. [Plays the "end explosion" sound on the ARP Odyssey.] And although this box actually isn't working very well—in fact, it's gone wrong—I think it makes a very good noise anyway, and we never throw anything away at the Workshop.

Used for Pea Soup, as specified in this page of Collins' official website and this page about Pea Soup.

"Countryman Phase Shifter"

The fabulous Countryman Model 968 Phase Shifter. Manufactured c. 1974, this circuit was the heart of my feedback piece Pea Soup. This specific box, which I bought on eBay in 2005 in a fit of nostalgia, had been owned by the legendary "Different Fur" recording studios in San Francisco.

"Nicolas Collins: About Pea Soup"

I composed Pea Soup while a student at Wesleyan University. A self-stabilizing network of analog circuitry (originally three Countryman Phase Shifters) nudges the pitch of audio feedback to a different resonant frequency every time the feedback starts to build. The familiar shriek is replaced with unstable patterns of hollow tones, a site-specific raga reflecting the acoustical personality of the room. These architectural melodies can be influenced by moving in the space, making other sounds, or even by letting in a draft of cold air. The piece existed both as an installation, responding to visitors, and in a concert version, in which people performed activities intended to influence the feedback.

In the late 1990s I tried to replicate the now unavailable Countrymen, and by 2002 developed a fair emulation in software, which I return to for minor tweaks on a regular basis. Thirty years on I began touring the piece again, and re-positioning what was a typical 1970s task-oriented work of strict Minimalism with a freer occasion for "improvising with architecture."