music  performances
A performance, in performing arts, generally comprises an event in which a performer or group of performers behave in a particular way for another group of people, the audience. Choral music and ballet are examples. Usually the performers participate in rehearsals beforehand. Afterwards audience members often applaud. After a performance, performance measurement sometimes occurs. Performance measurement is the process of collecting, analyzing and/or reporting information regarding the performance of an individual, group, organization, system or component.
Live performance events including theater, music, dance, opera, use sound production equipment and services like: staging, scenery, mechanicals, sound, lighting, video, special effects, transport, packaging, communications, costume and makeup to convince live audience members that there is no better place that they could be right now. This Live Event Support article provides information about many of the possible performance production support tools and services and how they relate to each other. Live performance events have a long history of using visual scenery, lighting, costume amplification and a shorter history of visual projection and sound amplification reinforcement. This article describes the technologies that have been used to amplify and reinforce Live events. 
An audio engineer is concerned with the recording, manipulation, mixing and reproduction of sound. Many audio engineers creatively use technologies to produce sound for film, radio, television, music, electronic products and computer games. Alternatively, the term audio engineer can refer to a scientist or engineer who develops new audio technologies working within the field of acoustical engineering.
Noted audio engineer Roger Nichols at a modern era recording console.
Audio engineers in research and development usually possess a bachelor's degree or higher qualification in acoustics, physics, computer science or another engineering discipline.
They might work in acoustic consultancy, specializing in architectural acoustics. Alternatively they might work in audio companies (e.g. headphone manufacturer), or other industries which need audio expertise (e.g. automobile manufacturer), or carry out research in a university. Some positions, such as faculty (academic staff) require a Doctor of Philosophy. In Germany a Toningenieur is an audio engineer who designs, builds and repairs audio systems
Live sound mixing is the process of electrically blending together multiple sound sources at a live event using a mixing console. Sounds used include those from instruments, voices, and pre-recorded material. Individual sources may be equalised and routed to effect processors to ultimately be amplified and reproduced via loudspeakers. The live sound engineer balances the various audio sources in a way that best suits the needs of the event
Audio engineering concerns the creative and practical aspects of sounds including speech and music, as well as the development of new audio technologies and advancing scientific understanding of audible sound.
Audio engineers working in research and development may come from backgrounds such as acoustics, computer science, broadcast engineering, physics, acoustical engineering and electronics. Audio engineering courses at university or college fall into two rough categories: (i) training in the creative use of audio as a sound engineer, and (ii) training in science or engineering which then allows students to pursue a career developing audio technologies. The second type of courses necessarily have the significant scientific and mathematical content needed to carry out research and development in audio engineering.