but concludes with a stronger cadence. More specifically, the basic idea 'returns' in bars 5–6 and then leads to a contrasting idea, which may or may not be based on that of the antecedent." Sub-Saharan music and music of the African diaspora Bell patterns The second definition of period in the New Harvard Dictionary of Music states: "A musical element that is in some way repeated," applying "to the units of any parameter of music that embody repetitions at any level." In some sub-Saharan music and music of the African diaspora, the bell pattern embodies this definition of period. The bell pattern (also known as a key pattern, guide pattern, phrasing referent, timeline, or asymmetrical timeline) is repeated throughout the entire piece, and is the principal unit of musical time and rhythmic structure by which all other elements are arranged. The period is often a single bar (four main beats). The seven-stroke standard bell pattern is one of the most commonly used representations of the musical period in sub-Saharan music. The first three strokes of the bell are antecedent, and the remaining four strokes are consequent. The consequent diametrically opposes the antecedent. Clave Cuban musicologist Emilio Grenet represents the period in two bars of 2/4. In explaining the structure of music guided by the five-stroke African bell pattern known in Cuba as clave (Spanish for 'key' or 'code'), Grenet uses what could be considered a definition of period: "We find that all its melodic design is constructed on a rhythmic pattern of two bars, as though both were only one, the first is antecedent, strong, and the second is consequent, weak." As Grenet and many others describe the period, the cross-rhythmic antecedent ('tresillo') is strong and the on-beat resolution is weak. This is the opposite of Western harmonic theory, where resolution is described as strong. Despite this difference, both the harmonic and rhythmic periods have consequent resolution. In simplest terms, that resolution occurs harmonically when the tonic is sounded, and in clave-based rhythm when the last main beat is sounded. Metric consonance is achieved when the last stroke of clave coincides with the last main beat (last quarter note) of the consequent bar. The antecedent bar has three strokes and is called the three-side of clave. The consequent bar has two strokes and is called the two-side. The three-side gives the impression of asking a question, which is answered by