Install alsamixergui by entering the following commands in the terminal:
sudo apt update sudo apt install alsamixergui
graphical soundcard mixer for ALSA soundcard driver
alsamixergui is an FLTK based mixer program for use with the ALSA soundcard drivers. It supports multiple soundcards with multiple devices. . alsamixergui is a frontend for alsamixer, written directly on top of the alsamixer source, leaving the original source intact, only adding a couple of ifdefs, and some calls to the gui part. It provides exactly the same functionality, but with a graphical user interface.