Your dream contains several themes and symbols that can provide insight into your current emotional state and experiences.

1. Return to Secondary School: Going back to school often reflects feelings of nostalgia or unresolved issues from that time in your life. It may indicate a desire to revisit past experiences or feelings of anxiety about current responsibilities and challenges.
2. Performance Anxiety: Practicing a song for a performance suggests you may be feeling pressure to succeed or showcase your talents in your waking life. This could be related to your studies, work, or personal projects. The last-minute nature of the performance may indicate feelings of being unprepared or overwhelmed.
3. Teeth Crumbling and Falling Out: Losing teeth in dreams is a common symbol often related to anxiety, vulnerability, or a fear of losing control. It can represent feelings of inadequacy or concerns about your appearance and self-image. The crumbling teeth might highlight feelings of failure or worry about not measuring up to expectations.
4. Drooling and Hiding: The uncontrollable drooling could symbolize feelings of embarrassment or a lack of control over your emotions or situations. This aspect of the dream may suggest that you are struggling with how you present yourself to others and that you fear judgment or criticism.
5. Difficulty Finding Chords: Returning to the piano but struggling to find the right chords might reflect your current struggles to express yourself or to find your place in a situation. It indicates a sense of frustration and confusion about how to move forward.

Overall, this dream may suggest that you're experiencing anxiety about performance and self-presentation, possibly reflecting pressures in your life. To address these feelings, it might be helpful to explore what areas in your life are causing stress and consider ways to manage those pressures. Practicing self-compassion and allowing yourself to be imperfect can also alleviate some anxiety.