The mandolin is the soprano member of the mandolin family, just as the violin is the soprano member of the violin family. Similar to the violin, the instrument scale length is typically about 13 inches (330 mm).
So what are the different types of mandolin that can be found? Well, below is a list of some of the main type of mandolin:
The mandola (US and Canada), termed the tenor mandola in Europe, Ireland and the UK, which is tuned to a fifth below the typical mandolin, in the same relationship as that of the viola to the violin. Some people also call this instrument the “alto mandola.” The instrument scale length is typically about 16.5 inches (420 mm). It is normally tuned like a viola, which is: C-G-D-A.
The octave mandolin (US and Canada), termed the octave mandola or mandole in Europe, Ireland, and the UK, which is tuned an octave lower than the mandolin. The instrument scale length is typically about 20 inches (500 mm), although such instruments with scales as short as 17 inches (430 mm) or as long as 21 inches (530 mm) are not unknown.
The mandocello, which is classically tuned to an octave and a fifth below the mandolin, in the same relationship as that of the cello to the violin: C-G-D-A. Today, it is quite frequent that it is restrung for octave mandolin tuning or the Irish bouzouki’s GDAD. The instrument scale length is typically about 25 inches (635 mm). Note that a violoncello scale is 27″ (686mm).
The Greek laouto is actually a mandocello, ordinarily tuned D-G-D-A, with half of each pair of the lower two courses that are being tuned an octave high on a lighter gauge string. The body is a staved bowl, the saddle-less bridge is glued to the flat face like most ouds and lutes, with mechanical tuners, steel strings and tied gut frets. Modern laoutos, as played on Crete, have the whole lower course tuned in octaves as well as being tuned a reentrant octave above the expected D. The instrument scale length is typically about 28 inches (712mm).
The mando-bass, has 4 single strings, rather than double courses, and it is tuned like a double bass. These were made by the Gibson company in the early twentieth century, but appear to have never been common. Most of the mandolin orchestras will prefer to use the ordinary double bass, rather than a specialized mandolin family instrument.
The piccolo or sopranino mandolin is a rare member of the mandolin family, tuned one octave above the tenor mandola and one fourth above the mandolin; the same relation as that of the piccolo or sopranino violin to the violin and viola. The instrument scale length is typically about 9.5 inches (240 mm).
The Irish bouzouki is also considered a member of the mandolin family; although it is derived from the Greek bouzouki, it is constructed like a flat backed mandolin and uses fifth-based tunings (most often GDAD, an octave below the mandolin, sometimes GDAE, ADAD or ADAE) in place of the guitar-like fourths-and-third tunings of the three- and four-course Greek bouzouki. Although the bouzouki’s bass course pairs are very often tuned in unison, on some instruments one of each pair is replaced with a lighter string and tuned in octaves, in the fashion of the 12-string guitar. Although occupying the same range as the octave mandolin/octave mandola, the Irish bouzouki is different from the former instrument by its longer scale length, typically from 22 inches (560 mm) to 24 inches (610 inches), although scales as long as 26 inches (660 mm), which is the usual Greek bouzouki scale, are not unknown.