mpcenc: 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/mpcenc - from package: musepack-tools

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

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