This is the 18th - yes, 18th - album from the apparently eternal Shonen Knife. Their story might be long, but it's not complicated. Some Japanese women liked The Ramones, so they made a band. Aside from a couple of line-up changes, that's pretty much it. Thirty-one years and counting.

The punk they're emulating may have been brash and angry, but Shonen Knife have always been anything but. This latest collection is no different. Pop Tune is, like all of its predecessors, as inoffensive as a teddy bear. Naoko, the guitarist, singer and only original member, has a voice as cute as a button. You can imagine her writing songs about sunshine or paperclips.

Oh wait, you don't have to. 'Sunshine' and 'Paper Clip' really are songs on the album. 'I can see some flowers everywhere', says one. 'So many clips in a plastic case', says the other. The music behind the words may have once qualified as 'rock', but it's long since been outgunned by even children's TV. Remember the X-Men cartoon's theme? Smoking riffs, compared to this.

It's actually hard to see how Shonen Knife have remained so innocent after three decades of touring. They've played in the world's grimiest venues, many times over. They have, we should assume, shared stages with fuck-ups and drug addicts. How can they write lines like, "When you go to an all-you-can-eat, remember to take some vegetables!" ('All You Can Eat') without a hint of cynicism? You start to wonder if they're playing up to their image, but to accuse them of that would be to say, utterly, that happiness and rock'n'roll can not coexist. Because if you can't believe a trio of smiling, 50-year-old Japanese women, who can you believe?

Pop Tune is a happy album. It's exactly the same as any of Shonen Knife's other 17 records, but it's still proud to be what it is. They're children who never grew up; punk's Lost Boys. Your average modern day cynics are going to struggle to embrace the harmonies, handclaps and lyrics about tie-dye shirts, but if they manage it they'll find a level of charm that can't be found anywhere else in music.