Equinox by Rick Dior is an intermediate level ensemble with a featured theremin soloist. The title of the piece is taken from the biannual crossing of the sun over the equator which results in night and day being of equal length on two days of the year. Shifting, crossing melodic motifs serve as countermelodies to the lead theremin melody and, at times, there are as many as four countermelodies crossing each other. The crossing of these percussion voices, be it rhythmic or harmonic, mimic the equinox event, with the theremin floating on top of these crossing motifs. Dior recommends using a Moog Theremini since it is easier to grasp than a standard theremin for the beginning player. He includes range and scale presets for the theremini as well. This piece comes as a professionally printed and bound score and includes individual parts in PDF format for printing or for tablet viewing.