About new stage genres in the music of the second half XX century

New musical and theatrical genres that demonstrate post-non-classical thinking are considered. The most common happening, performance instrumental theater. Genres considered differently by V. Petrov, M. Pereverzeva, Yu. Gnirenko Katunyan, but, however, without disclosing their ontology logical basis. main distinguishing features of the new stage forms openness structure, creative function performers temporal unlimitedness, which indicates rhizome composers. It is proposed to consider realities as non-linear, in particular dissipative, based on a non-linear type determinism – self-determinism. On its basis, rational construct established form self-organization (performer), or performing will, provide material with quality integrity. Alternative theater another have emerged era, post-modern era. presented alternative opera ballet, establish aesthetics consonance, antimimesis display (instead experience), well multivariant implementation concept (concert, stage, etc.). works American composer D. Cage, Russian Martynov, Belarusian composers Kuznetsov, L. Simakovich, A. Korotkina were selected analytical material.