It’s possible that ‘Sign “O” The Times’ (the single) had the same effect on one generation of music lovers as ‘Waterloo Sunset’, ‘Arnold Layne’, ‘Purple Haze’ or ‘Penny Lane/Strawberry Fields’ (all released between March and May 1967) did on another.

Released on 13 March 1987, it’s hard to think of another top 10 single of the 1980s with as much as space in it (and uncharacteristically deep reverb on Prince’s vocals, presumably utilising the famous Sunset Sound echo chamber). Apart from his guitar and voice, it was all performed on a Fairlight synth/sampler.

Adorned with a back cover featuring Cat Glover, the single drew lyrical inspiration from various news items read in The LA Times during the week of Monday 14 July 1986: Reagan’s ‘Star Wars’ program, the AIDS crisis, the investigation into January’s space shuttle disaster and the inner-city drug wars.

Lisa Coleman reports that she heard Prince’s amazing programmed drum groove blasting out of the venue speakers during a soundcheck in Denver in early July 1986.

Famously barred from releasing a three-album set by Warner Bros. – a process outlined in detail in Duane Tudahl’s wonderful recent book – Prince regrouped, quickly creating new material and then making the title track his new double album’s centrepiece.

Sign became the sound of summer 1987 in my corner of west London. Prince had been on my radar before – Parade was a definite sleeper – but this was it. And yet it still seems one of those ‘classic’ albums that gets talked about more than listened to.

So I listened to it. In one sitting. Probably for the first time in about five years. It’s probably even better than I remembered it. Has anyone ever captured a ‘party in the studio’ vibe better than Prince on ‘Housequake’ and ‘Play In The Sunshine’? And usually he only had Susannah Melvoin and engineer Susan Rogers for company. Of course this was in a sense a throwback to classic Little Richard and Chuck Berry, as well as James Brown tracks such as ‘Get Up Offa That Thing’.

He begins each side with groundbreaking tracks for him that took a while to record. We’ve discussed ‘Sign’. Then there was ‘It’, actually his first song exclusively using the Fairlight (apart from his guitar and vocals). Then ‘U Got The Look’, which was drastically sped up at the eleventh hour, ratcheted up a few semitones. Then ‘The Cross’, written and recorded the day after the infamous Los Angeles earthquake of 12 July 1986. Prince’s drums on this track speed up a lot – Rogers reportedly noticed but decided not to point it out.

Rogers also reports that she occasionally badgered Prince about the seemingly ‘lo-fi’ nature of these recordings, but he didn’t budge, and the album benefits from that ‘unfinished’ quality, even if it features a lot less bass than most modern music.

Sign features probably Prince’s greatest music, but we could all debate which tracks could have been left off. I could do without ‘It’, ‘Forever In My Life’, ‘Slow Love’, ‘The Cross’, ‘Adore’ (and would have preferred ‘Power Fantastic’, ‘Dream Factory’, ‘Crucial’, ‘Sexual Suicide’ and ‘Good Love’, but Prince had long jettisoned them by early 1987…).

Also why does the superb album design get short shrift? It’s a key part of the package. Hail photographer Jeff Katz and graphic designer Laura (niece of Tommy) LiPuma.