At the Paula Cooper Gallery for MATA’s 20th birthday celebration, Mexican percussionist Diego Espinosa faced the challenge of performing a 1967 work by Philip Glass, with the world-class composer seated several feet away. Instrument: an ordinary caterer’s foldup table. Soon in the cathedral style space, the sound of rhythmic scratching rose to the skylights. The piece, “1 x 1,” had been created on a kitchen table, Espinosa explained later, and he memorized the notes, applying them freely. Crouching down, he added the metal of the table’s spindly legs to the act, improvising on every surface. If a definition of “new music” were needed to kick off MATA’s week of experimental music concerts, this opening performance illuminates.