Jennifer Garner plays the saxophone to mark Reese Witherspoon’s birthday

Jennifer Garnerknew exactly what to get for the girl who has everything. The actress helped Reese Witherspoon mark her 42nd birthday on Thursday, March 22, with a very special musical tribute on Instagram.

“Hey, @reesewitherspoon! I don’t know why you’re on my mind today . . .,” Garner captioned her video. In the clip, the mother of three — clad in full in a full marching band outfit — plays “Happy Birthday to You” on her saxophone.

The self-proclaimed “band geek” proudly played the alto saxophone at John Adams Junior High in West Virginia.

“You know when you walk in a parade you have to really smoothly go heel-toe . . . because you don’t want to jostle your instrument. You want a steady gait,” she explained during a 2016 appearance on Late Night With Seth Meyers. “You want to key off with the person to your right because you want a straight line. You cannot mess around.”

Garner wasn’t the only one to give Witherspoon a shoutout on her special day. Her Wrinkle in Time costar Mindy Kaling shared a photo from the set, writing: “Happy birthday, queen, You make life so fun!”

Meanwhile, Zoe Salanda tweeted, “Happy Birthday @RWitherspoon! Hope today is as magical as you are!”

When Garner turns 46 next month, she can expect a special message from Witherspoon. Last year the Big Little Lies star posted a throwback picture with the caption: “Here’s looking’ at you, Jen! Happy birthday to my gorgeous friend #JenniferGarner who always laughs at my jokes and my bad dance moves. Love you!”

Witherspoon is currently shooting season 2 of Big Little Lies.