At this piece of mine, I have the pianist (at an upright piano, with the front lid removed) at a certain point holding down a chord with his left hand and with his right hand strumming the strings of the piano.
I'm looking for a way to notate this on the sheet music. Is there any way to do it, or should I simply use words to explain what he is to do?
This article may be helpful...
Ishii (2005) The Development of Extended Piano Techniques in Twentieth-Century American Music
Example from the article...
Helmut Lachenmann's Guero for solo piano is replete with plucks and strums, albeit without strummed pitched chords. So adapt his notation: on the staff for the strumming hand, draw a thick diagonal line showing a strum's duration, direction, and force (see 2:30 in the video). In a footnote, indicate that strums range only over undamped strings.
