A mandolin is a musical instrument. It commonly has four courses of doubled metal strings tuned in unison (8 strings), although five (10 strings) and six (12 strings) course versions also exist. The courses are normally tuned in a succession of perfect fifths. Strings run between mechanical tuning machines at the top of the neck to a tailpiece that anchors the other end of the strings. The strings are suspended over the neck and soundboard and pass over a floating bridge.The action of the strings on the bridge causes the soundboard to vibrate, producing sound.