The Finns haven't started rehearsals for their concert at Auckland Zoo just yet - they are scheduled for next week - but the discussions have certainly begun about which songs they'll be playing.
"That's as much part of it as playing," Liam nods, as the three of them sit down for a rare family interview, in a local cafe courtyard, birds tweeting appropriately in the background.
"We've pared it down to 19 songs I think, it was quite hard to do, to get it down to that," Tim laughs.
"Yeah, specially from 460. That was the shortlist," explains Liam. "There's probably 2000 currently in the database. We've got a Finn family computer that has all the songs and lyrics, and there's four thousand."
Neil: "Yeah Dad operates it, and he marks them all as well, they're all graded from one to 10."
So who does Finn senior give the most tens to?
"Well if you annoy him as a person, he takes marks off your songs, which is quite easy to do - if you call him at the wrong time for example," Liam answers.
"Dad used to mark accurately according to how he felt," Tim continues, "and some of them were dropping down to seven, and even six, and I think it was Mum who would say, 'Well you can't do that'. So they all started to move back up towards nine and 10."
"He's lost interest in marking them now," Neil adds, "which is slightly sad in a way, because I miss the marking. You can't help but feel we're not relevant in Cambridge anymore."
It seems all Finn family discussions must be like this - full of laughter and gentle ribbing, even-handed banter, and a shared sense of humour. Yet there's plenty of respect too, not just for elders, but for the musical prowess of everyone in the family, which is why they clearly get such pleasure from coming together for these occasional projects.
Jokes aside, there will be plenty of diversity in the setlist for their zoo concert - of course they're keen to play their well known hits, but they're also picking family favourites.
"It's a chance to look at a few different albums," Tim explains. "Liam and Elroy are both fans of the first Finn brothers album from the early 1990s, and there's a song on there called Angels Heap, and another one called Mood Swinging Man that they were lobbying for quite hard for a while. And then there are songs of Liam's that we all love and our kids are obsessed with, like Cold Feet and Burn Up The Road. Harper [Tim's son] kind of knows those songs already actually, and there's no piano on them, but maybe he could play on one of them, see what it sounds like in rehearsal."
Tim's 11-year-old daughter Elliot knows Burn Up The Road pretty well too - she even showed her Dad the proper strum pattern for it.
"I was doing a very relaxed, summery, chinga chinga ching, and her ears picked up immediately, and she came over and said, 'Dad, that's not how you strum! You hold the chords down and I'll strum.' Next minute it was way more intense. We might do that one acoustically right?"
"Yeah, but maybe she'll strum for you," Liam grins.
You might think they'd get a little competitive when it comes to all playing together - too many cooks sort of thing - but it seems they've learned to hear the strength in each other's style, and welcome the opportunity to hear someone else's interpretation. In fact they're biggest problem at the moment seems to be that everyone wants to play the drums.
"For whatever reason, everyone keeps going 'Can I play drums on that one?' It's been more of a fight to get to see who plays drums on each other's songs, and then Elroy [Liam's younger brother who is actually a drummer] is there too going, 'Well I'm playing drums obviously!'" Liam laughs.
"He doesn't mind if he gets to play bass though," Neil adds, "because all drummers want to be bass players or front men, and all front men want to be drummers or bass players."
This is their chance to turn all their usual roles on their heads, and it's clear all of them are revelling in the opportunity.
"Because it's a rare thing for us, there is a sense of occasion ... we make a pretty good sound when we all play together, and there's a lot of sympatico in the way that we play," Neil smiles. "There are differences too though for sure, I mean Liam has taken electric guitar further than I ever did. There were times when I was on stage trying to conjure up things that I hear Liam doing quite effortlessly now, so it's good that the generations are moving the game forward."
"It's all pedals," Liam says modestly.
"Pedals and just sheer bollocks really," Neil adds. "There's not a wasted note."
"Do you mean sheer bollocks or sheared bollocks?"
Laughter descends on the group momentarily, but it's not long before they're back to discussing their various writing styles, and stealing each others' ideas.
Tim really likes Liam's frequent use of a chord progression that rises a minor third, and finds himself using it from time to time. He's less enamoured with the way both Liam and Neil like to write in tricky keys with lots of flats or sharps.
"They like using the capo and open tunings, but those of us that are a bit remedial on the guitar, you know, we're struggling to find the right spot to put the capo to make it easy. I'm getting there except for in Burn Up The Road where there's that semitone shift and it just messes with you."
"You can always change the capo mid-song," Neil teases. "I saw Neil Hannon from Divine Comedy do that once and it looked like a really cool move, he effortlessly just pushed his capo up a few frets in the middle of the song, and then back down again."
"Maybe you can get Elliot to move the capo too."
There are a few other chord shapes which Liam reckons always end up reminding him of various other Finn songs.
"I've encountered that problem a few times where something sounds familiar when you're trying to write a song, and then you realise it sounds familiar because I'm ripping off one of these guys. But at least they won't sue me. Actually we should talk about this in private, but there is one particular that I've ripped off of yours Tim, I don't know if I've told you."
It's not the only story of internal family copyright issues they have either.
Neil: "The most uncanny story I've ever heard about with that fraternal family thing, was that Tim dreamed once that Liam was writing a song, and remembered it when he woke up, and ended up writing a song based around it. It was a really good song, but a very complex copyright situation."
"It's on piano I remember," Liam laughs. "I've got a recording of you [Tim] doing it shortly after you dreamt it, because you wanted to play it to me to see if I had any ideas for it, but I was on the road at the time, and didn't really have anything for you."
Neil laughs "Liam couldn't deal with it in this reality!
"Liam is actually owed a bit of money for various lyrics too. He was responsible for 'Here comes Mrs Hairy Legs' in Chocolate Cake, and also quite a few lines in Pineapple Head as well, which he's never really received credit for, or compensation.
"Well, he's had some compensation over the years, spaghetti bolognese dinners and so on."
Liam: "I've got it pretty good."
Tim admits that stealing lyrics out of the mouths of children is quite a good way to go too.
"Kids go through a stage, when they're quite young, learning language, where they're really good at lyrics, they come up with these nuggets, and songwriters have a mind like a steel trap, you know, if you become a parent, your child can give you this great material for your songs. It's quite scary."
It's that kind of involvement in the craft from a young age which has made the Finn family New Zealand's most-loved family of multi-generational musicians. Just like Tim and Neil were introduced to music as a part of daily life as they grew up in Te Awamutu, hearing live music in a very communal setting on a Friday night, Liam, Elroy, Harper, and Elliot, have all enjoyed a family life where picking up some drumsticks or a guitar and adding your voice to the fray felt completely natural.
"And it looked fun," Liam explains. "I think me and Elroy and Harper and Elliot wouldn't have gotten into music if we hadn't seen it to be so much fun. Because it is fun, but it's easy for it to stop being fun if you start taking it too seriously, and to grow up with the party aspect of it, and the fact that music does bring so much joy and euphoria to people, that was the luring aspect of it.
"And you could stay up later if you were joining in with the music, you didn't have to go to bed."
Though each of the three are all currently working on separate projects as well (Tim is working on a long-term project with an opera company, Neil has been doing some producing, and already has new songs in the works after releasing Dizzy Heights last year, and Liam is working on something top secret and confidential) it seems that getting together as a family unit to perform is helping to inspire all of them to keep moving forward creatively, and feels like a good springboard for 2015.
"It refreshes and emboldens us hopefully, because you suddenly realise that you can do it really well," Neil smiles, "and I never feel like that more so than when I'm playing with my family."
Liam: "Yeah it feels like the beginning of something as well - not that we're going to be doing this all the time, but it seems like since that last one [at the Powerstation], there's quite a few of us now, that it feels relatively natural and effortless to make it something really special. We're careful about not putting too much pressure on it, but I think it's exciting for all of us to get the chance to start feeling it out really, in a new way."
Five songs we're hanging out to hear the Finns play:
• Stuff & Nonsense by Split Enz
It's got some amazing chord progressions, Tim always sounds wonderful singing it, and we think Tim's son Harper could pull off a new inventive piano part while Liam's doing some crazy electric guitar tones and harmonics to give it a new flavour.
• Jump Your Bones by Liam Finn
Seeing as everyone in the Finn family wants to be a drummer at the moment, we figure this would be the perfect track for at least double, if not triple drummers, such is the intense, raucous, epic nature of this playful track from FOMO.
• Andy by Don McGlashan
Neil and Don once did a truly beautiful version of this touching song in the stairwell of Roundhead Studio for a Radio New Zealand session, and it gave everyone in the room (or stairwell) goosebumps. Sure, it's not a Finn family song, but it would be a very special moment to see Neil accompanied by Tim on this track.
• Respect by Aretha Franklin
At the Powerstation concert in 2013, Tim's 11-year-old daughter Elliot made a surprise guest appearance to sing this whopping great Aretha Franklin hit, and boy has that girl got pipes.
• She Will Have Her Way by Neil Finn
Neil's recent version with his current touring band recorded for Spotify Live Sessions was such an energetic, layered, rollicking good time that we definitely want to hear it live.
Who: Tim, Neil, and Liam Finn
Where and when: Performing a special one-off show at the Auckland Zoo on Friday February 27.
* Tickets available through Ticketmaster.