Type on a twelve-inch
A rack is browsed at arm's length and then from a step back, and from that step back a typeface has no counters, no fine strokes and no italics.
It has a silhouette and a colour, and that is all it has. Almost every sleeve is designed on a screen instead, at a size nobody will ever encounter it.
The first distance is arm's length, holding it, which is where every sleeve is designed and every proof is approved. At arm's length a twelve-inch is enormous. You can set eight-point type on it and it is perfectly legible, and designers do, constantly, because at arm's length it looks refined.
The second distance is across a shop. Three metres, at an angle, in a rack, with only the top forty millimetres showing above the divider, under a strip light, while somebody is flicking past at roughly one sleeve a second.