The room became the instrument.

At a concert in Woodstock, New York, in 1952, David Tudor sat at a piano and premiered John Cage's 4′33″. Across three movements, the performers make no intentional sounds. That description can sound like a trick, until you notice the difference between an instrument not playing and a room having nothing to hear. A concert hall does not become acoustically empty just because its pianist stops.

Cage's piece gives surrounding sounds a duration and a place inside a performance. A cough, a passing car or the small movement of a chair might normally be treated as an interruption. Within this frame, a listener can attend to them. The title names the length; it does not tell you what the experience will sound like. A performance in a library, beside a road and beneath trees cannot have the same audible contents.

Try a smaller exercise of your own: leave one minute without headphones or a recording. This is an observation prompt, not a reproduction of Cage's score. Notice a sound that stays constant, one that arrives suddenly and one you cannot locate. You may discover that your surroundings have layers you usually flatten into 'background'. You do not have to agree that every noise is music to find the experiment useful. An apparently empty space can contain a great deal once the expectation of a melody is removed. Attention is doing some of the work we normally assign to the composer.