Octave mandolin in unison. Alternate tunings exist in which the strings in some courses are tuned to octaves, rather than unisons, but this is more typical of the Irish Bouzouki. Usually, courses of 2 adjacent strings are doubled (tuned to the same pitch). The standard octave mandolin tuning is G2 G2 • D3 D3 • A3 A3 • E4 E4, so the lowest open strings are tuned to the lowest 'G' on the guitar, and the highest strings are tuned to the same 'E' as the highest string of the guitar. This tuning is one octave below the mandolin (or a fourth
Richter-tuned harmonica note downwards in pitch. This allows for every note on the XB-40 to be bent downwards a whole-tone or more, whereas on standard diatonics only certain notes (the higher-pitched in the cell) will bend at all. The other Richter-tuned harmonica of this kind is the Suzuki SUB30 Ultrabend. Where the XB-40 uses valves and a total of 40 reeds, the SUB30 takes a different approach. Each hole of the harmonica houses a third reed, totalling thirty reeds altogether and thus, where the harmonica draws its name. The third reed is dubbed a "sympathetic reed", tuned one tone below the pitch