A 4:1 audio mixer is a device that combines four audio input signals into one output signal. This type of mixer is commonly used in live sound settings, recording studios, and broadcasting. It allows users to control the volume, tone, and effects of each input, ensuring a balanced and polished final mix. These mixers typically feature individual channels for each input, along with a master control for the overall output. They can connect to various audio sources, such as microphones, instruments, and playback devices, making them versatile tools for audio production and performance.