This volume contains the only two pieces that Castillo wrote for the organ during the decade of the 1970s: the Coral y diferencias (1967) and the Sonata (1969).
The Coral y diferencias para órgano y cuerdas (Chorale and differences for organ and strings) was written in 1967, ten years after the composition of Suite para órgano, which appears in volume i of this collection.
It consists of fourteen variations on a choral theme of the composer’s own creation. Faithful to his usual criteria, it scrupulously respects the musical ôformö while expressing it in agile modern language.
The composer Tomás Marco considers this score û Castillo’s first concerted work organ û as ôimportantö; with certain obvious qualities such as ôthe mastery (M. Castillo’s) of the art of the variationö. Nevertheless, it is not as ambitious as the Sonata, which he wrote two years later and which was premiered on the Conservatory’s new organ.