In music, cinquillo is a special valuation group made up of five musical notes that can be equivalent to six or four of the same species. It is indicated with a five and a bracket on the figures it affects. When it is equivalent to six they will enter 5 in the place of 6 (deficient group) and therefore it is a group of special valuation by extension, since these 5 will have to be slower. If they are equivalent to four of the same species it will be a group (surplus) of special valuation by reduction, since when entering 5 in the place of 4, these 5 will have to be faster. Example: in a 2/4 bar, a sixteenth note belt is equivalent to a black one (5 instead of 4).
In general, instrumentalists consider it a more difficult resource to perform than a triplet, a sixteenth and even a quadrillo. This is because it is easier to play simultaneously three pulses against two, or four pulses against three, than five against two or four.
It is sometimes erroneously referred to as quintillo (as a diminutive of quinto), as is the case with the seisillo (which the RAE also accepts as sextillo, diminutive of sexto).