techincal question about john cagee

I haven't heard this, but you can get a percussive-ish sound from a piano by muting the strings; perhaps he had a pedal that did this

(that first "this" = the song you're referring to, obv.)

Cage used a number of techniques in his prepared piano pieces, including inserting rubber wedges, bolts, screws, piepans, wire, and wood between and alongside the strings of the piano. The pieces also included specific pedal directions to enhance the sonic effects of these preparations when particular notes were played. I'm not sure which modification was in use on the section to which you're referring, however.

ha saw this q when it was posted but tis like my brane didn't process it? On my LP from the record library (haven't got it with me so i can't check) he would, like nom says, place screws and bolts etc in certain places but I think it depends on the piece and so on.

henry cowell was the precursor for this kind of thing.

Julio is correct -- Cowell was Cage's teacher in the '30's and introduced him to the idea of manipulating the open strings of the piano to produce different effects (see, for instance, Cowell's "Aeolian Harp", which doesn't use the keyboard at all).

Cage invented the technique of preparing the strings to achieve percussive effects, which he first used on a piece called "The Bacchanale" (sp?), accompanying a Merce cunningham dance work. As there was no room for percussionists in the performance space, only a piano, Cage devised the preparation technique to replicate the sound of a percussion group. The other big influence here would probably be Lou Harrison, who had introduced Cage to gamelan music. The prepared piano pieces often evoke gamelan both sonically and rhythmically.