From an interview with Clash Music:

CLASH MUSIC: You say you often change your set-up and the way you do things, what did you change and get into for the Analord series?

APHEX TWIN: Most of it was sequenced on an MC4 and other analogue sequencers.

Martin Gore used a Roland MC-4 sequencer in the production of A Broken Frame. It is just visible at the bottom of the image.

From One Two Testing magazine, November 1982 (also the source of the image, http://www.muzines.co.uk/articles/when-the-wave-forms/4617#):

Time to change the subject. What's been the greatest advance in the studio?

Martin: 'I think probably the Roland MC4, that was a big breakthrough.'

The MC4 is the second in Roland's series of Microcomposers — very sophisticated computer-based sequencers that are able to control several synthesisers at once. Information is fed into them via a keypad on the front and with the right numbers you can dictate timing, pitch, duration and dynamics of each note, rub out the ones you don't want or rearrange whole sections to make up a song.

'We use it in the studio to run sequences and Danny has an old Roland SH-1 synth where each key has a number written on it in red. That's the number you put into the MC4 to get that note. It's also useful because I can take it home and work on a song, then bring it to the studio and play it back. Even if you don't use any of the riffs or sequences you've still got the length of the song programmed in.

'One of the disadvantages is that it won't run the PPG.'

'Yea,' continues an irate Andy. 'It's annoying that different synthesiser makers won't put in the right clocks and gates so you can use their equipment with someone else's. They all want you to carry on buying their gear, but every firm is good at some things and not at others so you'll always want to swap around.'

It's true that PPG are planning to bring out their own computer to operate the Wave, but right now, in Blackwing studio, that's no great help. Depeche did consider using the MC4 for live work, either alongside or possibly in place of the Teac tape. But it's the fear of road failure that keeps them off the idea.

'We have to be our own roadies at the airports. We each get a trolley,' explains Dave, 'and we see how the stuff comes down the chute: CRASH! I don't think the MC4 could stand it. If that went wrong on stage, you've had it. At least with a tape you can rewind and start again.'

Sakamoto uses the MC-4 circa 1982.

Vince Clarke using the MC-4 - Vince Clarke began using the MC-4 on Yazoo's debut album Upstairs at Eric's in 1982.

"Sometimes, I’d sample them and then use them on a track along with other sequencers. With this gear, I started building up my first studio tracks. I also acquired a Roland MC-4 sequencer that I used with my Roland Jupiter-4 and MC-202."

the Roland MC-4 can be seen behind Svein throughout this TOTP performance

In the March 1983 issue of EMM, Roland Orzabal discusses the utility of the Roland MC-4 MicroComposer for creating multi-layered sequences.

In an undated interview with Steelberry Clones, Daniel B. of Front 242 discussed his progression through music technology. Paraphrasing/translating for Daniel, the interviewer wrote:

Personally Daniel did not want to learn any instrument, although started as a drummer, so he ventured into the field of synthesizers. actually his first synthesizer was a Roland System 101 back in the 70’s. Things like the Fairlight was far too expensive, but the fact that Daniel got a job in a music shop allowed him to explore a lot of the new gear that came about, e.g. the Roland MC4 Micro Composer. (The MC-4 MicroComposer was an early microprocessor-based music sequencer released by the Roland Corporation. It could be programmed using the ten key numeric keyboard or a synthesizer keyboard using the keyboards control voltage and gate outputs.) So in summary Daniel says that his biggest influence was through the love of machines.

Here’s a photo of Steve Porcaro’s microcomposer sourced from an interview with KVR audio. He used the microcomposer on Michael Jackson’s Thriller. For example, the ostinato pattern in Human Nature, which he sequenced with the Jupiter-8.

In this profile from the May 1982 issue of Electronics & Music Maker magazine, Keith states that he used an MC-4.

MC4 is visible in the lower right corner.

Isao Tomita utilized the Roland MC-4 MicroComposer, as noted in the source detailing his work on "Tomita - Grand Canyon."