Irish bouzouki when having a longer scale length. The fifth course is usually either a lowest bass course tuned to C2 or D2 on an instrument with a long scale, or a highest treble course tuned to G4 or A4 on a shorter scale. Luthier Stefan Sobell, who coined the term "cittern" for his modern, mandolin-based instruments, originally used the term for short scale instruments irrespective of the number of their strings, but he now applies "cittern" to all 5 course instruments irrespective of scale length, and "octave mandolin" to all 4 course instruments, leaving out bouzouki entirely. Mandolin-family luthiers producing an
Irish bouzouki octave mandolin are more likely to use mandolin tuning machines and reproduce the details and styling of their American-style carved top mandolins. Some luthiers choose to refer to their clearly bouzouki-style instruments as octave mandolins, or even as mandocellos, despite the GDAD tuning. The octave mandolin is usually regarded as having a shorter scale length than the Irish bouzouki, in the vicinity of 20 to 23 inches (50 to 59 cm), while the scale length of the Irish bouzouki most often ranges from 24 to 25 inches (60 to 65 cm). Some instruments have scales as long as 26 or