“Smoke On the Water” by Deep Purple centers on a G minor tonality, but there’s some other stuff in there too. The opening riff features a ♭2nd interval and♭5th interval (ala the blues scale).
Here’s me teaching the Smoke On the Water riff.
The♭2nd is used again in the chorus for the A♭ chord. As far as the parent major scale, the song doesn’t fit into one key and actually has elements from all three minor modes. The chords in the verse, Gm and F, could fit in G Aeolian mode (B♭ major scale) or G Dorian mode (F major scale). The chorus uses a C major chord which is G Dorian and also an A♭ which is G Phrygian (E♭ major scale). Combining different keys like this is a form of modal interchange. If you want to play over it, best to keep it simple and just use the G minor pentatonic!
Here’s a video featuring Ann Klein playing the Smoke On the Water chords and guitar solo.
Excellent breakdown here. Very useful.