The ukulele is a guitar-like 4-string plucked instrument with a small size. In contrast to the guitar, the fourth (top) string is often octave and therefore tuned higher than the middle strings. This gives the ukulele its unmistakable, exotic sound. There are different models and moods. The classic ukulele, the soprano ukulele, is the smallest. Others are the concert, tenor and baritone ukuleles, which are getting bigger and have a deeper sound. There is the C-tuning (g'-c'-e'-a 'Hawaiian tuning) and D-tuning (a'-d'-fis'-h' classic tuning). A relatively new form is the bass ukulele. Strictly speaking, it is not a ukulele but a miniaturized electric or acoustic bass.