Final answer:
The instrument that accompanies the recitative secco in an opera is a harpsichord.
Step-by-step explanation:
The instrument that accompanies the recitative secco in an opera is a harpsichord.
Recitative secco is a vocal style in opera where the singer is accompanied by only a harpsichord or piano, playing chords to support the singer's voice. The harpsichord is a keyboard instrument that was commonly used during the Baroque period. It produces sound by plucking strings using a mechanism called a plectrum.
In contrast, the other options listed (piano, saxophone, and electric guitar) are not typically used in the accompaniment of recitative secco in opera.