Which scale degrees should two choir students maintain a drone on during sight-singing to instill a sense of tonic?

To instill a sense of tonic during sight-singing, the scale degrees that should be sustained in a drone are the first degree (do) and the fifth degree (sol) of the scale. This combination is particularly effective because it provides a strong harmonic foundation that clearly outlines the tonic chord. The tonic (do) is the root note, establishing the key center, while the dominant (sol), being the fifth, supports the tonality and emphasizes the resolution back to the tonic. This relationship reflects the foundational principles of harmony, where the tonic and dominant play crucial roles in establishing and reaffirming key signatures in music.

In contrast, other combinations like do and mi (the first and third degrees) or do and re (the first and second degrees) do not create as strong a sense of resolution or tonality as the tonic and dominant combination. While re and la (the second and sixth degrees) can contribute to melodic lines, they do not effectively establish the tonic. Thus, maintaining a drone on do and sol is the best choice for fostering a palpable sense of tonic during sight-singing.