To me the origins are in Glam Rock (bowie, cooper, the sweet, slade, t. rex), 70s hard rock (Aerosmith, Kiss, Zeppelin), early Heavy Metal (Sabbath, Judas Priest, Maiden, Motorhead), early rock (Stones, Who), and Arena Rock (Boston, Styx, Journey). The degree of each (or at all) depended on the group. Earlier bands had a more of a glam rock and early rock with heavy metal (they got their melodic ideas from early rock and glam rock), later bands had much more arena rock influence. It all depends on who classifies as a the first glam metal band. I think it did originate in LA as Quiet Riot, Van Halen, Dokken (all LA) were around in the 70s. Motley Crue and Quiet Riot are most often thought of as the bands that broke down the doors to mainstream sucess( both LA), it may depend on if you concider Def Leppard Glam or Kiss(kindof proto glam metal)full fledged glam bands at their inception. But also i hear,a certain LA Metal sound vs other places. LA bands most commonly had Eb standard tuning (GNR, LA Guns, Ratt, Van Halen, Wildside, Poison(after moving to LA/first album), Dokken, Odin,...) also with alot of LA bands, the rhythm style wasn't always strait (swung or layed back a bit a la Van Halen beautiful Girls). IF you listen to most of the Brit, Euro bands, they were most often in Standard Tuning with a straiter rhythm approach, many Bands from the SOuth (Southgand, Baton Rouge, Mcqueen Street, Tora Tora) had a certain rock n'rolly influence to them, with a certain groove and drawl. Just some stuff to chew on