Installing xmix package on Debian 9 (Stretch) is as easy as running the following command on terminal:
sudo apt-get update sudo apt-get install xmix
xmix package information
|distro||Debian 9 (Stretch)|
|description||X11-based interface to the Linux sound driver mixer|
More information about apt-get install
apt-get install is followed by one or more packages desired for installation or upgrading. Each package is a package name, not a fully qualified filename. All packages required by the package(s) specified for installation will also be retrieved and installed. The /etc/apt/sources.list file is used to locate the desired packages. If a hyphen is appended to the package name (with no intervening space), the identified package will be removed if it is installed. Similarly a plus sign can be used to designate a package to install. These latter features may be used to override decisions made by apt-get's conflict resolution system.