The term “temperament” often arises in classical-music circles in connection with the behavior of high-strung performers, but it also refers to the system of tuning to which a musical instrument is subjected. The ancient Greek philosopher-scientists (and figures who championed them later) liked to view musical harmonies as reflecting uncluttered mathematical relationships, but that translates awkwardly to the realm of real-world music-making. Over the years, musicians have experimented with countless ways to alter mathematically pure pitches through practical compromises that support the aspirations of composers and performers. On Sunday, Feb. 23, at 3 p.m., pianist Willis “Chip” Miller will perform on two dissimilarly tuned pianos to demonstrate how different temperaments can yield audibly different characteristics of tonal color and expressive suggestion. He will make his point by playing selections from Bach’s Well-Tempered Clavier, Mendelssohn’s Songs Without Words, preludes by Rachmaninoff, and études by Chopin. This free concert takes place in the Great Hall of Peterson Student Center at St. John’s College, 1160 Camino de Cruz Blanca. Call 505-984-6000 for further information.