Install aumix-gtk by entering the following commands in the terminal:
sudo apt update sudo apt install aumix-gtk
Simple mixer control program with GUI and text interfaces
aumix is a small, easy-to-use program to control the mixer of your sound card. It runs in text mode using the ncurses library, or from the command line (non-interactively). It can read default settings from a file, and it can also automatically save and restore the mixer settings at shutdown and boot. . Additionally this version can be run as a GTK+ app, i.e. with a graphical interface. It can also still run in text-only mode, though.