Modular electronic controllers for audio mixers, audio equipment, stage lighting, visual equipment; audio mixers; audio equipment, namely, surround sound systems, recording and playing devices for sound carriers, electric effects units for musical instruments, loudspeakers, subwoofers, audio amplifiers, signal processor for audio speakers, audio equalizer apparatus, audio circuits boards, limiters and compressors, electric audio playback units with lights and speakers, audio dubbing apparatus...