Phil was inspired by Bob Seger and Bruce Springsteen when he wrote Boys Are Back In Town.
And of course there are plenty of Thin Lizzy songs that are not straightforward three chord rockers.
A decent hard rock song generally needs four or five different chords! Less is dumbed-down AC/DC, more is in danger of trespassing PROG territory.
For a hard rock band, Thin Lizzy were relatively major chord happy, that and Phil's baritone vocals really set them apart from many others in a similar field. His vocal style has grown on me over the decades, I didn't much like it first, back in the seventies I had a penchant for high-pitched screamers such as Ian Gillan, David Byron, Dan McCafferty, Ozzy or Rob Halford, I just thought that their vocals towered more "above" the music. Thin Lizzy did not have that, but to their credit they knew how to arrange their music so that Phil's lower register singing wasn't drowned out.
