I never heard Salvatori presented as anything by Bungie but a jobber. He had been the lesser composer (working underneath Martin) at Bungie for years before Destiny, and stayed with the company during the Microsoft exodus. It boggles my mind that Bungie would suddenly want or try to present him as anything else because I reckon they never actually treated him that well.

No, it was Paul McCartney (of Beatles / Wings fame). Activision likely pushed for them to have a 'big' name associated with the game, and the new-guard at Bungie seemed gaga over the idea as well. Given the music that made it into the game, it is very obvious to my ear O'Donnell was the primary composer. The beef as I understood it then was that Bungie was pushing for giving McCartney top billing despite all of his contributions being vague and without direct attribution song to song. I still have no clue what music or musical themes are supposed to have been his, though I admit I stopped caring about Bungie during the early phases of Destiny so if they've revealed that information since, very well.

The music sounds like O'Donnell music, you can draw a straight line from Halo (especially ODST) to Destiny very easily. They have to convince me it was otherwise and I certainly didn't see it at the time.