volti-mixer: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/volti-mixer - from package: volti

You may install the required package with command apt-get install {package}
Error in other languages:
volti-mixer: bevel nie gevind nie
volti-mixer: comandă negăsită
volti-mixer: comando não encontrado
volti-mixer: commande introuvable
volti-mixer: command not found
volti-mixer: käsku ei ole
volti-mixer: không tìm thấy lệnh
volti-mixer: komanda nerasta
volti-mixer: Kommando nicht gefunden.
volti-mixer: kommandot finns inte
volti-mixer: komut yok
volti-mixer: nie znaleziono polecenia
volti-mixer: níor aimsíodh an t-ordú
volti-mixer: no se encontró la orden
volti-mixer: no s'ha trobat l'ordre
volti-mixer: opdracht niet gevonden
volti-mixer: parancs nem található
volti-mixer: perintah tidak ditemukan
volti-mixer: príkaz nenájdený
volti-mixer: příkaz nenalezen
volti-mixer: команда не найдена
volti-mixer: командата не е открита
volti-mixer: 命令找不到
volti-mixer: コマンドが見つかりません