The band is getting together in the second book of this laugh-out-loud graphic chapter book series starring four musical instruments in their first year at Band Camp! It's Cordelia's birthday but she feels left out when the group seems to be keeping secrets (her surprise party!).

Cordelia is feeling down after losing her footing during the tug-of-war competition, so Kaylee, Zook, and Trey decide to throw her a surprise birthday party. Determined not to disappoint her friends again for the next challenge, a group hike, Cordelia does all she can to prepare, but all the rest of the instruments' secret planning for the party is making Cordelia feel even more left out. Who will end up surprising who when the day of the hike comes around?