As I recall, this is a whole lot of fun.
The movie is a paste-up of various "suggestive" film items from the 1930s and 40's, presented without commentary.
A large proportion of the film consists of "soundies" - short black & white films made for an early kind of "video jukebox". So we get to see Fats Waller doing the title song, for instance. But there are also pieces from sound shorts, and features - an eclectic collection, from both sides of the Atlantic.
What sticks in my mind is Sophie Tucker in a night-club in about 1930: splendidly sharp images, and excellent sound from the stage p.a. Because most footage of 20's dancebands comes from silent films, it's often 'souped up' with montage. This crisp footage, from one camera, with excellent sound, gives a sense of a real event.
OK, so far, so good.
For the next part, I may well be imagining this. But I seem to recall that the U.S.P. of this film was that, interspersed between the musical numbers were rather tame and clumsy vintage porn films...
The result is, in fact, very 70s: the baby-boomers' exciting discovery that there was actually sex before the Second World War.
But with the passage of time, I suspect that the material contained within this movie has become more and more Martian (like Al Jolson movies). In 1974, the culture that produced the various soundies and the pornies was still familiar; we all knew lots of people who had been young back then.
But I suspect modern audiences might find it all totally, totally surreal.