On most Fridays, the grounds of ʻIolani Palace fill with the sound of the Royal Hawaiian Band. The band presents free concerts there from noon to 1 p.m.; check the ʻIolani Palace concert listing before you go, since dates can change.
King Kamehameha III founded the band in 1836. I see it as a public Honolulu institution with royal history behind it, not a hotel attraction built around a visitor schedule. Follow current Palace guidance while you are on the grounds.
I would build this into a Palace visit or a downtown walk. The concert lands in the middle of Friday lunch hour, on grounds many Waikīkī visitors never reach, and its calendar can shift. That makes it easy to miss and well worth planning around.
