Twilight Undulations (2001) was written in memory of American composer Robert Starer (1924–2001) who died on April 22, 2001. The piece is based on the plainsong Ad dominum dum tribularer clamavi, intended to be sung at vespers on the Sunday after the Feast of Corpus Christi. The plainsong is never heard directly in its original form but rather in a transformed state. This transformed plainsong is presented at the outset and then in a reverse canon with itself at the octave. The melodic material is heard over an undulating ostinato in manuals and a drone with punctuations in the pedals.