mpc: command not found

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/mpc - from package: mpc

You may install the required package with command apt-get install {package}

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