What is "prog jazz?"

My general 'style' of composing (especially in the last few years) is something I call ‘Progressive Jazz’ or ‘Prog Jazz.’ Not to confuse the issue too much...we all know that jazz in and of itself is a ‘progressive’ art form (marked by the nature of improvisation alone), and continues evolving (even though sadly, the number of venues to play it in continue to decline too rapidly). In this instance, I am coming at jazz in a different way…so, you know how the term ‘Prog Rock’ is applied to rock music – which contains elements of classical and jazz embedded within that genre, right? ‘Prog Jazz’ is coming at things in essentially the same way, and is my method of explaining writing the compositional elements from the jazz point of view first, then fusing harder-hitting rock/classical properties into the jazz afterwards – which, I don’t think up until now, has been properly addressed. This makes it a ‘jazzier’ element than Prog Rock at the outset by default, as I am starting the composition with jazz sensibilities from the baseline…jazz harmony/melody/rhythm and then putting that gumbo into a mostly rock and/or classical context. Well, at least that is the hope anyway, as long as music is continuously getting placed in little boxes, defining certain genres. It's jazz that can go wherever it likes, without any structural restrictions - but wherever it goes, it has to make sense in respect to the entirety of the song.”

— Brian Grace - May 2022