A rich program of classic works was on the menu for The Aptos Keyboard Series at St. John’s Episcopal Church in Aptos on January 13. Pianist Kate Liu took advantage of the warm acoustics of the church to create an atmosphere of quiet moods and colorful displays of sounds. Beethoven’s late Sonata No. 31, Op. 110, engages the listener much as do the same composer’s late string quartets, with tuneful passages and complex textures. Ms. Liu emphasized the lyrical qualities throughout with a beautiful singing tone. Even the fugue subjects were clearly apparent in the final movement. Two Beethoven characteristics were plumbed for dramatic tension, that is, the dynamic contrasts between loud and soft, and the use of silences. Actors know that a quiet delivery can demand more attention from the audience than a forceful one. And musicians know that a quiet phrase draws the listener into the action. This was a technique used by Ms. Liu throughout her program.