Here’s another rare groove, this time by The Constellations, released in 1968. Despite their starry name, they never hit the heights but they left their mark with this Northern Soul classic.

It’s hard for me to choose between the two sides of what seems almost to be their only single – I Don’t Know and I Didn’t Know How To.

The former just gets the edge because of the Philly-style string arrangement by Pat Jaques, who engineered the great O’Jays album Back On Top the same year.

Jaques was the president and chief engineer of New York’s Broadway Recording Studio, suggesting that’s where this was recorded – though it came out on Chicago’s Gemini Star label.

The only other single I can track down by The Constellations is a version of Easy To Be Hard, a big ballad from the once-controversial stage musical Hair, though the best known version of that is by Three Dog Night.