Taylor Swift uses the same four-chord progression in many of her songs. Photo: Graham Denholm/TAS24
What does Taylor Swift have in common with the Beatles, Beyonce and Elton John?
Many of her smash hits are based around the same four-chord progression, which an academic says gives songs a certain "emotional flow".
The now-defunct music comedy trio Axis of Awesome highlighted the chords in a comedy festival routine in 2009, singing a mashup of Top 40 singles that use the same progression.
They range from 'Don't Stop Believing' by Journey and 'Let It Be' by the Beatles to 'Africa' by Toto and 'Paparazzi' by Lady Gaga.
Taylor Swift and the Axis chord progression
Sydney Conservation of Music lecturer Dr Jadey O'Regan told Sunday Morning the 'Axis chords' - as they are now known - follow a simple I, V, VI, IV pattern.
If playing in the key of C, for example, the chords would be C, G, A minor, F.
O'Regan said many artists - from the Cranberries to Green Day - used the same chord progression, but Swift seemed to have a "specific fondness for it".
Not counting the tracks on her newest album, The Tortured Poets Department, it could be found in 21 of her songs, including 'Love Story', 'Champagne Problems', 'Out of the Woods', 'I Knew You Were Trouble' and 'All Too Well'.
O'Regan said the chords were a hit with listeners because they took them on an emotional journey.
"I think it comes down to its familiarity. Even if you're not a musical person, you already know a likeliness of where chords are going to end up because we've just consumed so much pop music for all of our lives," she said.
"It has a little bit to do with what's called a cadence - the relationship between one chord to another. So from that I to V, that's a really familiar cadence ... when it gets to that VI, that A minor, it's like 'ooh, some tension, feeling a bit emotional' ... and then it's resolved down to that F which is the IV, and we're like 'oh we're back home again'.
"It sort of has an emotional flow, those four chords, and we feel it when we hear it."
O'Regan said many genres of music shared chord progressions.
Much early blues music used the same three chords over 12 bars, while the 'doo-wop progression' in the 1940s and '50s "defined an entire genre".
That was a similar progression to the Axis chords, she said: I, VI, II, V.
"It's been in thousands and thousands of songs."
One of the most amazing things about the Axis chord progression was that it could be "used in so many different ways in terms of the emotional weight of what the lyrics are doing", O'Regan said.
"With Taylor Swift, it's absolutely the way she performs it, it's the way she sings it, it's also the autobiographical stuff in the lyrics that's really important."
The chord progression was a simple way to anchor a song without overwhelming the listener, allowing a songwriter to "layer" complicated lyrics and gymnastic vocals on top, she said.
That meant musicians like Swift could achieve "this really beautiful balance between the familiar and the novel".