Advanced Linux Sound Architecture (ALSA) is a software framework and part of the Linux kernel that provides an API for sound card device drivers. Some of the goals of the ALSA project at its inception were automatic configuration of sound-card hardware and graceful handling of multiple sound devices in a system.
alsamixer is a graphical mixer program for the ALSA, that is used to configure sound settings and adjust the volume. It has an ncurses user interface and does not require the X Window System. It supports multiple sound cards with multiple devices.
By default, after rebooting PC all changes to its configurations will back to default.

To save your settings use this command:

sudo alsactl store

It will save alsamixer configurations to /var/lib/alsa/asound.state file, which gets loaded automaticly every startup.
You can also use a custom configuration file, but after every reboot it should be loaded manually.

Save alsamixer configurations to custom file:

alsactl --file ~/.config/asound.state store

Load alsamixer configurations from custom file:

alsactl --file ~/.config/asound.state restore