Can a song contain three different scales on it ???
Songs dont really ‘contain’ scales. Rather, the harmony and melody in a song generally draws on groups of notes from a scale. Eg. If a song is in the Key of A Major, it will, generally, contain chords and notes from the A major scale.
If a song changes key, then those chord/ notes will come from this new scale. Key changes are common in genres like jazz.
If you were improvising/soloing over a piece, then there would be an element of choice as to which scales/ scales you might draw from. With a genre like the Blues in particular, the mixing of major and minor pentatonic/ blues scales is very common. Or even using a note ‘palette’, rather than a scale.
Hope this helps.
To add to what Shane said if your talking soloing or improvising you can follow the chord changes. So rather than playing just the parent scale of the key the song is in you change scale with each chord change. For a 1 4 5 in A over the A chord you would play the A major scale over the D chord you would play the D major scale and over the E you would play the E major scale. You can also use either pentatonic scales or arpeggios relative to each Chord. You can also make it more complicated and use modes but that’s a whole other story.
Songs can contain whatever the creator wants.
Changes in key or timing, use of multiple scales
Funny that “No Rules, Just Right” is the slogan of Outback Restaurants here in the States - Aussie themed Steakhouses & that there are so many “Aussies” here in the Community!!! Maybe I’m just being a bit quirky here, but I think that’s hilarious!!!