Hey, what's that sound: Zithers and autoharps

It's the sound that unites Orson Welles and PJ Harvey
PJ Harvey at the Troxy, London in February 2011
Harping on ... PJ Harvey at the Troxy, London in February 2011. Photograph: Matt Kent/WireImage

What is it? Well. A zither is technically any stringed instrument that has the feature of the strings not extending beyond the soundhole or resonator of the instrument (unlike, say, a guitar, where the strings stretch out into a neck). This includes a lot of instruments with which you may not be familiar, such as the koto, hammered dulcimer, Appalachian dulcimer, psaltery, cimbalom, guqin, guzheng and santur, as well as the piano or harpsichord. We're going to look mainly at the fretted concert zither, and its younger cousin the autoharp.

Who uses them? The fretted zither probably first came to international recognition scuttling through Viennese alleyways in Carol Reed film of Graham Greene's The Third Man, and it's still the zither's most famous role. The Carter Family – and the hands of Carter matriarch Mother Maybelle, in particular – made the autoharp a symbol of American country music in the 20s. More recently, PJ Harvey's experiments with modified autoharps saw her write pretty much all of Let England Shake on the instrument – contributing to the album's strange dislocations and preoccupations with national identity.

How do they work? Though the instrument exists in myriad fretless forms under a plethora of different names, the fretted zither is played by holding down chords on the guitar-like fretboard with one hand, and variously plucking and strumming strings assigned for either chord or melody purposes. The autoharp simplified the technique by removing the fretboard and replacing it with a series of "chord bars" that, when depressed, dampen down any strings not relevant to the intended chord.

Where do they come from? The oldest known zither was a Chinese guqin, found in a royal tomb in 1977, but which was entombed in 403 BC. German inventor Karl August Gütter patented his "Volkszither" in 1883, the same year that German immigrant Charles F Zimmerman patented Gütter's design as the autoharp in Philadelphia, and which went on to become a classic instrument of Americana.

Why are they classic? The zither can move smoothly between classical and folk music, and even approximate something like the woozy lilt of a Hawaiian lap steel guitar. Both the autoharp and zither have a distinctive, spidery, high register rattling sound, which can be evocative, especially in soundtrack work.

What is the best ever zither or autoharp song? Never ones to shy away from the obvious, it's Anton Karas's Harry Lime Theme, and while you should check out old Carter Family standards such as Wildwood Flower for the autoharp, people really are getting quite excited about that PJ Harvey album …

Five facts and things

For a long time, zitherists have been perplexed when transcribing The Harry Lime Theme. It wasn't until Carol Reed revealed many years later that Karas had exploited an early use of overdubbing when recording the piece – layering on a harmony track of him playing the theme in thirds over the initial take – that the physics of the seemingly impossible-to-play piece made sense.

Karas was not really a composer, but a skilled busker who Carol Reed discovered playing outside a Viennese cafe, during a break in shooting for the The Third Man. Fascinated by the strange instrument he was playing, Reed whisked the reluctant Karas back to his London flat, where he would force him to work 14-hour days for 12 weeks, composing sounds that the director insisted match up perfectly with onscreen visual action.

The Harry Lime Theme went on to sell half a million copies. Karas toured the world, becoming drinking buddies with Orson Welles and Gina Lollobrigida, even performing for Emperor Hirohito of Japan – yet he remained bitterly resentful of his success, complaining he had been forced to work on the film "like a slave".

Prior to the Carter Family, the autoharp was played with the instrument resting on the lap of the player. The Carters saw Grand Ole Opry star Cecil Null playing the instrument upright, and this led to the standing-up style of playing that is standard today.

After giving three old autoharps to an instrument repairman in Dorset, with the instruction "to put them into the strangest chord configurations he could possibly think of", PJ Harvey found that song melodies would suggest themselves as she sang her poems about England over odd tunings, contributing to a dreamlike, timeless feel.