It can be performed by any kind and number of instruments or voices. Only one instrument must play ad libitum the series with the last three or four notes (right) at random, but returning always to A flat. All other instruments and voices can be well tuned or fluctuate within a very small interval above and below the notes frequency of the instrument playing ad libitum: they can’t play more than five notes of the series for each performance.
— Roberto Donnini, instructions for Tunedless, 1977
The first drafter draws a not straight vertical line as long as possible. The second drafter draws a line next to the first one, trying to copy it. The third drafter does the same, as do as many drafters as possible. Then the first drafter, followed by the others, copies the last line drawn until both ends of the wall are reached.
— Sol LeWitt, instructions for Wall Drawing #123: Copied Lines, 1972
[Cross-posted at Scattered Work]