Continuity mistake: During the song 'Fabulous', by the swimming pool, Sharpay's shoes disappear, then reappear.
Continuity mistake: At Lava Springs, when Fulton hands Sharpay the marker (to autograph the talent show fliers) it is capless, but in the close-up as she signs her initials the pink cap is on the marker, but then it vanishes again. (00:11:35)
Continuity mistake: When Chad and Troy show up to caddy for the Evans family, the positions of Ryan and his mother, as well as the golf club bags, change depending on camera angle. The shadows they all cast also repeatedly change.
Continuity mistake: During Sharpay's version of "You Are the Music In Me" after she tosses her red jacket atop the piano it moves from front to side, again and again, during the song. (01:12:25)
Visible crew/equipment: After arriving at Lava Springs, when Sharpay signs her initials on the last two fliers in the wideshot, the reflection of the camera and crewmember are reflected on the surface of the Star Dazzle trophy, right beside Ryan's (blue shirt) reflection on its right. (00:11:45)
Continuity mistake: During "Everyday" Troy's microphone keeps switching hands.
Answer: It's a Musical. Instruments that aren't shown are always playing like this in these types of movies.