Final answer:
Option D: A mixer is the device used to control multiple audio sources like boundary mics, lead actors, or playback, enabling sound engineers to manage and combine several audio channels.
Step-by-step explanation:
The device that controls multiple audio sources, whether they be boundary microphones, lead actors, or playback, is a mixer. Audio mixers allow sound engineers to adjust the volume, tone, and dynamics of several audio channels and combine them into a single or multiple output signal. This is particularly useful in live performances, recording studios, broadcasting, and film production, where balancing and shaping the sound of the different audio sources is crucial. Mixers vary in complexity from simple units with a few channels to complex consoles with the capability to manage extensive live orchestras or multiple audio inputs in a studio setting.
To control multiple live sources like boundary mics, lead actors, or playback, the correct option would be Mixer. A mixer is an audio device that allows you to combine and control the audio signals from multiple sources. It provides the ability to adjust the volume levels, apply effects, and make specific changes to each source individually or collectively. By connecting the sources to different inputs on the mixer, you can have control over all those sources in one central place.