Electric guitar strings are made of ferrous metal because the electric guitar pickup directly senses the vibration of the string magnetically. They are made of usually steel plated with a nickel alloy.

For Acoustic guitar strings Bronze or Phosphor Bronze alloy is used, giving a better acoustic tone. Because the guitar does not rely on magnetic pick-ups non-ferrous metals may be used. The core wire is still made of steel (hence 'steel string' guitars), but the outer winding on the 'wound' strings is made of bronze.

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