The cuatro is any of several Latin American instruments of the guitar or lute families. Many cuatros are smaller than a guitar. Cuatro means four in Spanish, although current instruments often have more than four strings. The cuatro is found in Puerto Rico and in South America, and other territories of the West Indies. Certain variants are considered the national instrument of some countries (e.g., Venezuela). Its 15th century predecessor was the Portuguese Cavaquinho, which, like the cuatro had four strings. 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. 
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 traditional D tuning of the ukulele, 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 five strings or six 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).
Puerto Rico cuatros
The Puerto Rican cuatro is shaped more like a violin 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 Cuatro): all have ten 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 jelly-bean shaped body; a Cuatro Sonero, which has 15 strings in five courses of three 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 Cuatro"), is similar to a Cuban Tres, but with 4 courses of doubled strings, instead of the usual 3. It is usually tuned G4 G3•C4 C4•E4 E4•A4 A4.
- "Instrumentos Musicales de Venezuela: Cuatro". Diccionario Multimedia de Historia de Venezuela. Fundación Polar.
- Fredy Reyna: Alfa Beta Cuatro - Monte Avila Editores 1994
- Alejandro Bruzual: Fredy Reyna - Ensayo biográfico - Alter Libris 1999
- Chord and instructional guides
- Tobe A. Richards (2007). The Venezuelan Cuatro Chord Bible: ADF#B Standard Tuning 1,728 Chords'. Cabot Books. ISBN 978-1-906207-00-7.
- Tobe A. Richards (2007). The Puerto Rican Cuatro Chord Bible: BEADG Standard Tuning 1,728 Chords. Cabot Books. ISBN 978-1-906207-06-9.
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