What Taylor Swift's secret musical weapon has to do with Aussie ...

You know you're doing something right as a musician when a particular chord or chord progression gets named after you.

Take for instance the Hendrix Chord (that's a dominant seven chord with a sharp ninth), which the great guitarist dropped into songs such as Purple Haze, Voodoo Child (Slight Return), and Foxy Lady.

Similarly there's the Hard Day's Night chord, which has been the subject of intense debate and mathematical dissection, and is still something of a mystery (but play a G7 with a suspended fourth and you're pretty much there).

And then there's the Axis Progression — a run of four chords known by a few different names, but typically named after Aussie music-comedy trio Axis Of Awesome.

Their 2009 Melbourne International Comedy Festival routine noting that the key to musical stardom was a "Four Chord" song mashes up dozens of hits, all of which use the same chord progression or a slight variation thereof.

Over the years, their festival performance and the official music video have gone viral, racking up a combined total of more than 132 million views, leading to the now-defunct comedy trio getting their names attached to this common chord progression.

In musical theory parlance, the progression in question goes I-V-vi-IV — in the key of C, that translates to C-G-A minor-F.

Using that progression (or a vi-IV-I-V variation — that's A minor-F-C-G, so basically the same progression starting at the third chord), Axis Of Awesome were able to mash together more than 80 hit songs over the years in their ever-evolving routine.

Wikipedia (which includes variations that start at F or G instead of the A minor or C — so IV-I-V-vi or V-vi-IV-I) has a list of over 160 popular songs.

Meanwhile YouTuber/pianist David Bennett has compiled a list of almost 450 songs that use the Axis Progression.

These include everything from Journey's Don't Stop Believin' and Missy Higgins' Scar to The Beatles' Let It Be and Avril Lavigne's Complicated, from The Cranberries' Zombie and Alphaville's Forever Young to Men At Work's Down Under and John Denver's Take Me Home, Country Roads, from Frozen's Let It Go and The Lion King's Can You Feel The Love Tonight? to Adele's Someone Like You and Green Day's When I Come Around.

And a lot of acts don't just use it once.

According to Bennett, Blink-182 has used the Axis Progression in 15 songs, while Avril Lavigne has used it in nine, leading some people to refer to the run of chords as the Pop-Punk Progression.

Maybe it should be renamed the Swift Progression — Bennett says the most prevalent purveyor of the progression is Taylor Swift, who uses it in 21 songs (this doesn't include her latest album, which was released on Friday).

It's in Love Story, All Too Well, Champagne Problems, The Archer, Out Of The Woods, Teardrops On My Guitar, I Knew You Were Trouble and a bunch more.

And if you count some of the other variations where the progression starts at a different chord, it takes the total up to 39 songs.

Swift has also used a similar progression — the I-V-ii-IV — in 20 different songs.

This progression has only one chord different — so instead of being C-G-A minor-F if it's in the key of C, it would be C-G-D minor-F.

Re-using chord progressions is nothing new.

The entire genre of blues music is built on some variation of a single three-chord cluster — the I, IV and V chords (or C, F and G if you're in the key of C).

That's not just one artist reusing the same progression — that's a whole genre; literally thousands and thousands of musicians, all using some version of a single progression.

Sydney Conservatorium of Music lecturer in contemporary music Jadey O'Regan said the ubiquitousness of the Axis Progression is part of its appeal — it's a hook for listeners because "we know where we're going … and it feels good when we finally get there".

It also invites the audience to focus on other elements while conjuring a familiar emotion, Dr O'Regan said.

"If you had a song that had a crazy chord progression, amazing complicated lyrics and rhythm, changes in tempo — you can't [focus on] it all at once.

"A simple chord progression like this allows space in a song for other things to become more important … [or] to be expressive in different ways.

"For someone like Taylor Swift, the lyrics are really important, her performance of those lyrics is super important.

"For others it might be some production techniques that are really important, it might have a really cool rhythm.

"That's the power of an amazing chord progression — it allows so many different interpretations."

Swift's trick is to take the same progression or a close variation thereof, and make it feel somewhat different through her instrumentation, lyrics, melody (the notes she sings over the chords) and rhythm (when those notes and chords are played).

Take for instance, Out Of The Woods, which uses an insistent one-note melody over its propulsive chorus full of low synths, thumping percussion and reverb-drenched backing vocals.

Compare that with All Too Well, with its plaintive chorus hook, its intimate stream-of-consciousness storytelling, more organic instrumentation, and wandering yet emotive melody.

Also check out Champagne Problems, a more stripped-back approach to the progression driven by simple piano chords and a low-key hook.

Same chords, three very different songs, but all with that same haunting emotion at their core.

Dr O'Regan said the Axis Progression left "a lot of options open for melody", but the power of it largely came from the transition from one chord to the next.

"It has little cadences — a finishing feeling, essentially.

"And they're relatively strong cadences too — from the I to V, that feels really great, then we get a kind of emotional moment from the V to the vi so we have some feelings there, and then it feels so nice when we resolve to that IV and come back to the I to set us off on the progression again."

So is this a bad thing?

As Bennett noted in his analysis, "it's very easy to look at this and think this is a very boring or very lazy approach to songwriting".

"But there's also an element of 'if it ain't broke, don't fix it,'" he said.

"Taylor Swift is obviously a very successful artist and she obviously hasn't been hampered by the fact she keeps using the same chord progression.

"If anything, that might be one of the selling points of her music — if you enjoy these chord progressions then even though the songs might all start sounding quite similar, if you like the sound of that chord progression, then that won't necessarily be a complaint for you.

"Chord progressions are ultimately like colours — they are sets of colours that we can use as a foundation to create something more.

"A chord progression alone is not a song, and therefore recycling the same chord progression is not necessarily a bad thing."

Dr O'Regan agrees.

"If you think of early folk or early country music, often it was only three chords," she said.

"Same with the blues — it's a I-IV-V usually — and [part of] the reason for that is the words are there to shine."

She said the Axis Progression was actually an example of diversity within music, not repetition.

"That's something I love about pop music," Dr O'Regan said.

"You don't have to know all the chords — if you have four, look what you can make, look at all the hundreds of songs that come out of a chord progression like this.

"It really shows the beauty and craft of a great pop song, that you could take this same musical material and it can be expanded in all these different beautiful ways, from Let It Be by The Beatles to Bad Blood by Taylor Swift."