Like a lot of terms 'avant' is unsatisfactory but it has its uses. You usually know straight away if a jazz release is avant. It might be 'free jazz' it might have a noisy anarchic flourish to it. It might not conform to any rules. But the one element when you speak of jazz in terms of avant is that it has a strong improvisational angle.
So what makes it different to say other forms of jazz when improvisation is present there as well?
The differences lie in the extremity of the methods: 'free improv', also labelled under avant, for instance can and usually does involve no preparation in terms of prior composition. The performance is the composition, the interplay is the composition. But sometimes you get similar-sounding music that involves some element of composition or a mix of the two and it is usually the latter that makes up your typical avant composition.
Avant is more accepted and known about now than ever before. But it is not a one size fits all affair. Recent examples in these pages include
Listen to the above and you can realise what a big music avant is, full of individuality and not a single easily calculated style at all.
But to journey back to the beginning of avant you can get a clue where the music has its history and motivations. I'd choose the music of Ornette Coleman, Paul Bley, Cecil Taylor, late-period John Coltrane, Albert Ayler and Pharoah Sanders as the beginning of avant jazz, or 'free jazz' if you prefer. How avant has changed since is quite instructive but often still especially when saxophone is concerned the towering influence of Coleman and Coltrane are present and discernible.
You get certain later innovators who have also made an impact on the music and the next generation looks to them rather than the initial wave. Take Peter Brötzmann with his noisy raucous style, or Evan Parker with his precise, elaboratem explorations. But think when Keith Jarrett delivers his free improvisations on his solo albums you might think you are a world away from what Brötzmann and Parker are doing. But they all share in common the real time spontaneity and in the moment aspirations of free-jazz.
Avant is not everyone's cup of tea I should point out. It is not always easily digested because it isn't 'function music' in the way that a trio playing standards can be. It does not provide easy, soothing, answers and does not come in neat packaging. It aims to smash barriers and be ahead of the pack and it often is. But just as often it fails miserably and you get a generic sound that like every other style has its short cuts and hacks and somehow as a listener you know what is coming next. Avant has changed jazz for the better over the years and it will change it again whatever label you care to put on it and that is why it remains, to defer once again to Ornette Coleman, the shape of jazz to come.