Image copyright EPA Image caption The Pet Shop Boys are currently taking their elaborate stage show on tour

The Pet Shop Boys are a band of two halves - Neil and Chris; serious suits and silly headgear; a glorious '80s pop past and a constantly reimagined electronic future.

As singer Neil Tennant talks about a new series of reissued albums and an unheard track, those contrasts - which have always kept the band interesting - are as apparent as ever.

He looks back at how they have always looked forward. He has a lingering affection for old-fashioned physical music while admitting to succumbing to Spotify.

He doesn't like Ed Sheeran but says the singer should be allowed to dominate the charts. He wants you to buy one set of reissues but says not to bother with another.

Media playback is unsupported on your device Media caption Listen to the Pet Shop Boys' demo version of One-Way Street

The ones he's on the phone to talk about are 1999's Nightlife, 2002's Release and 2006's Fundamental, which are being remastered and reissued this month with copious bonus tracks.

One of those is One-Way Street, a previously unreleased demo from the Fundamental sessions, which Tennant says he offered to Bananarama at the time - but has now decided he rather likes.

Their first six albums, which were re-released with similar bonus discs in 2001, are also getting another reissue. But if you already own the first remastered versions, you can save your money, the singer suggests.

Image copyright EPA Image caption Neil (left) and Chris are reissuing all 11 albums they released on Parlophone Records

Does going through the vaults bring back memories?

It brings back a lot of good memories. It was a lot of fun and people often ask Chris [Lowe] and I how the whole thing has lasted so long. We always have the same answer, because it's true: We actually really enjoy going to the studio and writing songs together.

It is work but it's also play, and I think when you listen to the newly reissued stuff you can see that we write in different styles and we experiment and we always write more stuff than we need for an album.

Do these albums strike you as being better or worse than you'd remembered them?

Happily, they seem to me to be better than I remember. When you work on an album and do promotion for it, you can get fed up with the whole thing after a while. And then you don't really listen to it again very much because you've spent so long making it and then talking about it.

Listening back to Fundamental, I felt really pleased because it's quite an epic album and it's the only time we ever made an album which has got a strong concept.

We wanted to make an album that reflected what the world was like in the wake of 9/11, the Iraq war and the increasing surveillance techniques used by governments on their own people. It was a paranoid period and actually I think it expresses it quite well.

Image caption The duo's UK number ones include West End Girls, It's A Sin and Always On My Mind

Tell me about the unreleased song, One-Way Street.

In our studio we have a bookcase and One Way Street is the title of a book by the famous philosopher Walter Benjamin which, I hasten to add, I'd never actually read.

Chris was playing something on the keyboards and I saw this book and thought, "that's a good title". Actually it's got a catchy chorus. We offered it to Bananarama, who were making a new album. We gave it to them and they rejected it!

The reason we didn't put it out was because I thought the metaphor of a one way street - that something was predestined - was maybe a bit contrived. But listening to it all these years later it's very catchy.

Your first six albums are also being remastered again - how much difference will there be?

Well, it's a controversial thing in some ways because I think records should just get louder. If you bought the collection in 2001, I would suggest you don't buy them again because I think it's a bit ridiculous really. It's exactly the same tracks and the same packaging and the same booklet, it's just that they've been mastered again.

I asked our mastering engineer, 'Do you think you can make them sound better than they did in 2001?' And he said, "Yes we can, definitely." And part of me is even slightly sceptical about that. You're not getting any extra tracks or anything. Stick to your old ones, that's my advice.

Image copyright PA Image caption "Listening to a piece of music requires a certain amount of commitment"

These CDs are physical objects with nice booklets - what do you think of the instant and disposable nature of digital music?

I think having access to everything is amazing. I use Spotify myself sometimes but I also think that what it does is it makes pop music a very casual experience.

Just like reading a book, listening to a piece of music requires a certain amount of commitment from the listener to get the full enjoyment out of it. The ethos of Spotify works against that. When I'm at my house in the north of England, that's the only place I drive a car and I play CDs. Sometimes I've only got one CD.

Always the same one?

No, I change them but sometimes I get locked into an old Joni Mitchell album or something like that. I listen to Hejira relentlessly. Or I started listening to Sgt Pepper relentlessly.

What do you think about the new chart rules (which saw some of Ed Sheeran's songs leave the chart)?

Someone at some point decided what weight streaming should have on the chart. I don't know about that. But if Ed Sheeran has got 39 out of the 40 tracks or whatever then good for Ed Sheeran. If someone is having a moment of phenomenal success then good for them.

Don't think, "oh that can't be right so I'm going to change the chart". I think it's a bit weird. Unless, of course, the whole streaming thing is too weighted. I don't know.

They've limited each artist to only three tracks.

But why? I'm not a fan of Ed Sheeran but I think it's amazing he's done that. I don't think they should change the rules because they don't like it. As though Ed Sheeran's success is some sort of chart virus.

They were mostly album tracks.

Well, the question is, in the world of streaming, what is a single? A single is based on a 45rpm piece of vinyl.

Actually on this last album and probably the album before, every single we've put out has been number one in the CD singles chart. At one point we had three singles in the top 10 of the CD singles sales chart! Not many people put out CD singles, apparently.

Do you listen to current pop?

The album I've listened to this year has been The xx's album, which I listen to in the car up in Durham quite a lot. And I listen to quite a lot of electronic music. I don't listen to that much pop music, actually, but I'll do precisely what I criticised people for doing: I'll flick through things on Spotify.

Image copyright Neil Tennant Image caption Spanish fans greeted Tennant in home-made Pet Shop Boys pointy hats

Your 63rd birthday was on Monday and you posted a photo of lots of fans in Pet Shop Boys pointy hats.

When we arrived at the stage door at the Teatro Real in Madrid there were all these fans outside who had made pointy hats. They also had T-shirts in the style of the Super album saying, "Happy birthday Neil."

It's very touching when people do that. And it's sort of surreal. And when we came out of the gig, there were even more - there was a huge crowd of people and they all sang happy birthday in Spanish.

What's next?

We've got this tour which we're doing until the middle of October, when we end up in South America, which is where we started. And after that I don't know what we're doing. Isn't that great? But something will probably turn up.

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