qmp3join: 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/qmp3join - from package: quelcom

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

Error in other languages:
qmp3join: bevel nie gevind nie
qmp3join: comandă negăsită
qmp3join: comando não encontrado
qmp3join: commande introuvable
qmp3join: command not found
qmp3join: käsku ei ole
qmp3join: không tìm thấy lệnh
qmp3join: komanda nerasta
qmp3join: Kommando nicht gefunden.
qmp3join: kommandot finns inte
qmp3join: komut yok
qmp3join: nie znaleziono polecenia
qmp3join: níor aimsíodh an t-ordú
qmp3join: no se encontró la orden
qmp3join: no s'ha trobat l'ordre
qmp3join: opdracht niet gevonden
qmp3join: parancs nem található
qmp3join: perintah tidak ditemukan
qmp3join: príkaz nenájdený
qmp3join: příkaz nenalezen
qmp3join: команда не найдена
qmp3join: командата не е открита
qmp3join: 命令找不到
qmp3join: コマンドが見つかりません