mp3cd: 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/mp3cd - from package: mp3cd

You may install the required package with command apt-get install {package}
Error in other languages:
mp3cd: bevel nie gevind nie
mp3cd: comandă negăsită
mp3cd: comando não encontrado
mp3cd: commande introuvable
mp3cd: command not found
mp3cd: käsku ei ole
mp3cd: không tìm thấy lệnh
mp3cd: komanda nerasta
mp3cd: Kommando nicht gefunden.
mp3cd: kommandot finns inte
mp3cd: komut yok
mp3cd: nie znaleziono polecenia
mp3cd: níor aimsíodh an t-ordú
mp3cd: no se encontró la orden
mp3cd: no s'ha trobat l'ordre
mp3cd: opdracht niet gevonden
mp3cd: parancs nem található
mp3cd: perintah tidak ditemukan
mp3cd: príkaz nenájdený
mp3cd: příkaz nenalezen
mp3cd: команда не найдена
mp3cd: командата не е открита
mp3cd: 命令找不到
mp3cd: コマンドが見つかりません