It’s the stereotypical piano accompaniment to silent movies. The left hand plays the melody, and the right hand plays rapidly-alternating notes, like a trill but the two notes are farther apart (e.g. a sixth).
Tremolo. It’s not restricted to the piano - a similar rapid alternation between notes can be played on most instruments, and also a tremolo can be a rapid repition of a single note, especially on string instruments.
Yeah, but he meant what’s the term for playing the tremolo with the right hand and the melody with the left? Not that I know the answer…
Oh, there’s no specific term for that.