Voices, instruments, resonators, amplifiers, processors, mixers, loudspeakers, air, architecture, ambient noise, ears (auricles, canals, membranes, cavities, fluids, ossicles, cochleas, nerves), brains, bodies.*
Memory, imagination, notation, recording, training, practice, habit, preference, style, ideology, belief, taste, commitment.
Authority, institution, impressario, arranger, librarian, contractor, section leader, conductor, manager, bookkeeper, banker, producer, presenter, sound designer, editor, publisher, copyright holder, licensor, lawmaker, lawyer, broadcasting authority, censor.**
*Not to mention bone conduction, cochlear bypasses and direct electrical stimulation of the brain with transduced acoustical signals; Maryanne Amacher advocated a "post-cochlear listening".
**Not to mention parents, teachers, scholars, reviewers, critics, polemnicists.