What do the letters placed above the music indicate?

The letters placed above the music typically indicate the chords to be played. This is a common practice in various types of musical notation, especially in lead sheets and chord charts, where the music is accompanied by chord symbols that tell the performer which harmonies to play. These symbols provide essential information for musicians, particularly in genres like jazz, pop, and rock, where improvisation and harmonic accompaniment are key aspects of performance. Recognizing chord symbols allows a performer to interpret and play along with the music effectively.

Understanding the purpose of the other options provides context; while instrument indications would guide performers on specific parts, tempo markings would define the speed of the piece, and dynamic markings would convey the volume changes desired in the performance. However, the letters above the music primarily serve to communicate which chords to play, making 'what chords to play' the correct interpretation of their function.