Not a Giallo

Agree. Totally a slasher.

Freddy Krueger without Robert Englund is like a unicorn without a horn.

Love it, but yeah it's a slasher. The only giallo elements are the use of brightly colored backdrops in some of the sets.

I agree. A Slasher it is.

The slasher-giallo dualism is kind of a false one, as for Italian audiences any thriller (whether it is made in Italy or not) is considered a 'giallo': in the Italian language, 'giallo' is a catch-all term for thrillers of any description, even regardless of what country they were made in. (The Italians call the films that US and UK fans refer to as gialli, 'thrilling all'italiana' - Italian-style thrillers - which is arguably a better label for them.)

There were a fair few Italian thrillers (gialli) of the 1980s that adopted the traits of the US slasher film (eg, SOTTO IL VESTITO NIENTE) - and there were also some Italian thrillers (we could call them gialli) of the 1970s that predated the US slasher movie (eg, Bava's REAZIONE A CATENA; L'ASSASSINO HA RISERVATO NOVE POLTRONE, which has quite a few similarities with STAGE FRIGHT - if you've not seen that one, check it out, it's pretty good :) ).

For my money, STAGEFRIGHT is best classified as a late-period thrilling all'italiana that, like a fair few 1980s examples of the Italian-style thriller, incorporated elements of the bodycount/slasher film as a means of improving foreign sales. I don't think that makes it 'not' a giallo, as the giallo/thrilling all'italiana is such a nebulous subgenre anyway, including all kinds of very different films from 'straight' Agatha Christie-type thrillers to the more supernatural-oriented thrillers :)

'What does it matter what you say about people?'
Touch of Evil (Orson Welles, 1958).