Is the flamenco part in Queen's Innuendo a generic flamenco or is it based on some composer's flamenco (or other piece of music) or was it composed by Queen "from scratch" and has no references to other flamencos?
Flamenco starts on 3:33.
The spanish flamenco part was not composed by Queen, but improvised by an external musician, Steve Howe, invited for this song.
Wikipedia article about the song (according to Prog Magazine) says:
Inside, there’s Freddie, Brian and Roger all sitting together. They go: ‘Let’s play you the album’. Of course, I’m hearing it for the first time […] And they saved "Innuendo" itself until last. They played it and I was fucking blown away. They all chimed in: ‘We want some crazy Spanish guitar flying around over the top. Improvise!’ I started noodling around on the guitar, and it was pretty tough. After a couple of hours, I thought: ‘I’ve bitten off more than I can chew here’. I had to learn a bit of the structure, work out what the chordal roots were, where you had to fall if you did a mad run in the distance; you have to know where you’re going. But it got towards evening, and we’d doodled and I’d noodled, and it turned out to be really good fun. We have this beautiful dinner, we go back to the studio and have a listen. And they go: ‘That’s great. That’s what we wanted’.
Another source, Chronicle Live says about Steve Howe:
You also played the Flamenco solo on Queens No.1 hit Innuendo. How did you become involved with that?
Brian had his shot with it and had done what he’d wanted to do with it but thought that someone else could race about with it and add some excitement to those structures. They jokingly said I could do a bit of Paco De Lucia with it. I could see what they were after so I did some improvising and they loved it. I was so proud to be on that record.