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.Wikipedia ...

At that point, Styx unveiled 1975’s “Equinox” before jettisoning Curulewski and picking up another melodic young gunslinger, Tommy Shaw, who with Young keeps the flame going today.