The prelude uses a ternary meter subdivided into triplets. In measure 29, the beats are reorganized into a two-beat pattern, which is similar to a hemiola rhythm when two 3/4 measures are grouped into a 6/4 measure:
Something similar happens in measure 65. This time, the melodic rhythm uses half notes to prepare for the end of the prelude:
© 2019 José Rodríguez Alvira. Published by teoria.com