By the mid 20th century the Flamenco guitar was well defined. Cypress back and sides are used for their brighter sound and the way in which each note had an abrupt rise and decay.
The sustain of rosewood only muddles the sound of the fast picado runs. Wooden tuning pegs were used for economy and also to lightened the head, however modern metal machine heads are becoming the standard.
A low action is used, even if it means some buzzing of the strings, to facilitate speed.
A light overall construction is employed to the point of fragility to foster a bright sound. The resulting instrument is much sharper and "more flamenco".
Typically, the flamenco guitarist will not play over or near the sound hole, but back near the bridge. The result is a tough steely sound that's a crucial part of the flamenco style.
Many flamenco players seek out negra guitars, with rosewood back and sides rather than the traditional cypress. It is said these guitars offer the superior projection of a classical, while their lighter construction retains the bright and edgy sound of a traditional flamenco guitar.
The traditional "blondes" are the still the most popular with their immediacy and their muy flamenco sound.