It's Ralph Bakshi, being Bakshi. A filmmaker with more conventional ideas of storytelling would be incapable of this film. Bakshi just went ahead and made it.

It's about four men in America whose lives are all about music. Father, son, grandson and great-grandson. The first one (Zalmie) is a Russian immigrant, fleeing to New York to escape the pogroms. His father was a rabbi, killed by the Cossacks got him, while his mother dies not long after in what appears to be the 1911 Triangle Shirtwaist Factory Fire. Zalmie will be 17 in 1917, making him the same age as the century and so I assumed we were going to follow his life through to old age. Nope. Zalmie gets involved in the nightclub business, sometimes performing on the stage although "it's the music I love". This being the 1920s, this gets him involved with gangsters.

Of course Bakshi's charging head-first at the music, the social issues and the violence. That's why he's making this film. It's about juxtaposition, with music being the thread that joins it all together. The music he's chosen is immense, representing an entire era. Scott Joplin, George Gershwin, Cole Porter... but there's also World War One and gangland killings, some rotoscoped from The Public Enemy.

Then Zalmie has a son, Benny. Our focus moves to him, even though for the time being Zalmie's still alive. (He knows some unpleasant people, so it would be unsafe to reach any firm conclusions about what happens to him after we stop following his story.) Benny begets Tony, who then begets Pete. When the film reaches 1981, it ends.

This film's not easy on its audience. It doesn't have a plot in the normal sense. People live their lives, none of them particularly likeable, then vanish to be replaced by a new generation that's probably going to be even harder to care about. Only one of the four isn't in some way a criminal.

However it's vivid. This film has youth in its blood. Old men disappear. Music never stops evolving and driving us onward, propelled by these young men who'll otherwise leave very little mark on the world, except possibly a bloodstain. There are bullets, bombings and lethal overdoses. There are two world wars, in which of course people get shot. It's bleak and savage, with one of our four protagonists becoming the kind of bum who's soon going to be drinking meths in a doorway... and then his son finding different kinds of depths yet again.

Yet the music is to die for. We go from Benny Goodman and his orchestra to Bob Dylan, Jimi Hendrix, The Doors and The Sex Pistols.

Stylistically, it's not holding back. It's almost entirely rotoscoped, but to say that is to gloss over the sheer richness of what Bakshi's doing. He'll throw in newsreel footage, impressionistic paintings and raw pencils in a caricature style. He doesn't let you settle. He's in your face, making this most aggressively artificial of media seem unvarnished and real. Even the rotoscoping is pushing the boundaries of what's normally possible in what's essentially a money-saving shortcut, with some surprisingly subtle acting being evoked. You can often look at the animation and judge the live-action performances that are being used as source material. The actress playing the Grace Slick/Janis Joplin character, for instance, is full of interesting facial quirks.

There's something one almost never sees in the character design. I think each new son shows the influence of his mother in his features. Benny is good-looking because his mother was too, while Tony for his part has a touch of ugliness that's faintly sinister. Think of his mother's relatives and you'll know immediately where that comes from.

It also has some dazzling dialogue. It feels like some of Bakshi's other films, the ones where he just went out with a tape recorder and captured real conversations, thus yielding scenes that don't really have a conventional dramatic point but are nonetheless capturing a sort of asphalt poetry. The "I'm a dishwasher" conversation has a brilliance, for instance. "Your brains is falling out!" "Did you get your quarter? Did the brain fairy leave you a quarter last night?"

To be honest, I found it hard work. Sometimes the film pushes you away. However it doesn't know how to let up and eventually I found myself being dragged along by sheer accumulated momentum. It's abandoning conventional plotting, but you've got to admire its guts, if nothing else. Every era is explosively vivid, although the 1960s in particular are everything you'd expect from Bakshi. It's a film that's mainlining all the greatest music of its century, but it's also screaming in your face.