Equinox is the fifth studio album by American rock band Styx, released in December 1975. The lead single "Lorelei" became Styx's second US Top 40 hit.

Doug Sax was an American mastering engineer from Los Angeles, California. He mastered three of The Doors' albums, including their 1967 debut; six of Pink Floyd's albums, including The Wall; Ray Charles' multiple-Grammy winner Genius Loves Company in 2004, and Bob Dylan's 36th studio album Shadows in the Night in 2015.