David Mancuso starts the first ever record pool (a means for record companies to distribute promos to DJs). Promo 12 Inches appear with Calhoun’s ‘Dance Dance Dance’ rumored the first.
So "disco version" or "disco mix" means primarily that the record is longer
than the version released for radio play, though it may also mean that the
cut is specifically mixed for a "hotter," brighter sound. Disco DJs are much
more concerned with the technical quality of the records they play than their
radio counterparts, rejecting otherwise danceable singles because of the
deadness of their mix or their loss of distinction at high volumes. This
passion for quality has had its effect: Both Atlantic and Scepter have put
selected single cuts on 12-inch discs at 33 1/3 for best reproduction at top
volume. -- Vince Aletti in Rolling Stone Magazine, 8/28/75
