Aquila is rightly so placed in the crossover Prog section as this album is not actual prog rock. There are some prog elements though. The omnipresent sax and occasional flute is one of the things I feel is related to prog rock.
The music is rock music with lots of organ and sax. Ralph Denyer is an ok singer in my book, nothing special but not bad. The music reminds me of the english band Audience which have almost the same concept ( without the organ), so if youยดre into Audience try this one out. Audience have a better singer though.
The prog elements are most clearly displayed in The Aquila suite which very typically prog rock is divided into movements. Itยดs still basic rock, but with some organ and sax soloing put in there. The whole Suite ends quite symphonic without ever being symphonic prog though.