The Southern Arizona Symphony Orchestra presents the operetta The Merry Widow at 3 p.m., Sunday, April 18. The performance will be sung by costumed members of the Southern Arizona Opera Company. Nicholas Mariscol will also perform the first movement of Lalo's Cello Concerto. $20; free for ages 17 and younger. Visit www.sasomusic.org for tickets. Call 323-7166 for more information.