noun, noun or participle which takes 'suru'
A musical performance by two people, or the piece itself. Can also be used figuratively for any paired activity. The する form is common for 'to perform a duet'.
彼らはピアノとバイオリンでデュエットを演奏した。
They performed a duet on piano and violin.
結婚式で新郎新婦が
The bride and groom sang a duet at the wedding.