The cuatro is a family of Latin American instruments found in South America, and in Puerto Rico and other parts of the West Indies. Although some have viola-like shapes, many cuatros resemble a small to mid-sized classical guitar.
Cuatro means four in Spanish; the instrument's 15th century predecessor was the Portuguese cavaquinho which has four strings, like the original cuatro (modern cuatros often have more than four strings).
Certain variants are considered the national instrument of some countries (e.g., Venezuela). The cuatro is widely used in ensembles in Jamaica, Mexico, and Surinam to accompany singing and dancing. In Trinidad and Tobago it accompanies Parang singers. In Puerto Rico and Venezuela, the cuatro is an ensemble instrument for secular and religious music, and is played at parties and traditional gatherings.
Modern cuatros come a variety of sizes and shapes, and number of strings. Cuatros can either have single-strings, like a guitar, or double- or triple-coursed strings like a mandolin, and vary in size from a large mandolin or small guitar, to the size of a full-size guitar. Depending on their particular stringing, cuatros are part of the guitar or mandolin subfamilies of the lute family.
The cuatro of Venezuela has four single nylon strings, tuned (A4 D5 F♯5 B4) or (A3 D4 F♯4 B3). It is similar in shape and tuning to the ukulele, but their character and playing technique are vastly different. It is tuned in a similar fashion to the ukulele's traditional D tuning, but the B is an octave lower. Consequently, the same fingering can be used to shape the chords, but it produces a different inversion of each chord. There are variations on this instrument, having 5 strings or 6 strings.
Other Venezuelan cuatro variants include: cinco cuatro (5 strings in 4 courses); seis cinco (6 strings in 5 courses); cinco y medio (5 strings and a short extra string from the top of the body); cuatro y medio (4 strings plus a short extra string); and octavo (8 strings in 4 double courses).
The Puerto Rican cuatro is shaped more like a viola than a guitar, and is the most familiar of the three instruments of the Puerto Rican orquesta jíbara (i.e., the cuatro, the tiple and the bordonua). The Puerto Rican cuatro has ten strings in five courses, tuned in fourths from low to high, with B and E in octaves and A, D, and G in unisons: B3+B2 E4+E3 A3+A3 D4+D4 G4+G4.
Several sizes of the instrument exist, including a cuatro soprano, cuatro alto, cuatro tradicional (the standard instrument, also called cuatro tenor), and cuatro bajo (bass): All have 10 strings and are tuned in fourths. There is also a cuatro lírico (lyrical cuatro), which is about the size of the tenor, but has a deep jellybean-shaped body; a cuatro sonero, which has 15 strings in 5 courses of 3 strings each; and a seis, which is a cuatro tradicional with an added two-string course (usually a lower course), giving it a total of 12 strings in 6 courses.
The Cuban cuatro (cuatro Cubano, or tres tuatro), is similar to a Cuban tres, but with 4 courses of doubled strings, instead of the usual 3 courses. It is usually tuned G4+G3 C4+C4 E4+E4 A4+A4.