Niall on AH put up a shot of the
inside of his Mutronics Mutator. I realized I haven't put up a post on the Mutator, so why not. Title link takes you to the Mutator site with samples and more.

"The Mutator is a stereo analogue filter and envelope follower with full control facilities. It contains two independent voltage controlled filters similar to those found in analogue synthesizers, which can be used to treat any external sound source. Each filter can be controlled from its own associated low frequency oscillator (LFO) and/or its own envelope follower section, which extracts the envelope contour of an input signal and applies it to control the cut-off frequency of the filter."

Note that chip in the middle is an SSM2045. I checked
Synthech and
Sequencer.de to see what other synths might have used the chip. I only found it on Sequencer.de for the Solton SM100 used as a VCA/VCF. If you know what else the chip was used on, feel free to comment.
Click here for a full shot of the above.
Update via the comments:
"Someone who was there at the time said...
Little-known fact:
Contrary to the information given by the Mutronics website, the Mutator was conceived, designed, and the first production runs hand-built and tested by a British guy called Nigel Bradbury who started Mutronics with London-based studio-owner Mark Lusardi in the mid 1990s.
With his partner and their new-born daughter remaining in their home-town of Oxford, Nigel worked on the Mutator in London for £50 a week, almost all of which was taken up by the rent for his grimy week-day accommodation and bus transport back home at the weekends. Eventually it became uneconomic and uncomfortable for him to continue spending so much time away from his family, and Nigel parted company with Mutronics with nothing but a second-hand Mutator (previously owned by Duran Duran, no less) to show for his hard work and creativity.
His part in conceiving and creating what is probably the best analog filter unit available remains unmentioned on the Mutronics website and promotional materials, and some people feel he was unfairly treated by his business partners. To this day he refuses to discuss this period of his life.
Nigel currently designs medical electronic equipment in Oxfordshire."
Update: more updates in the comments.