ncmpcpp: 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/ncmpcpp - from package: ncmpcpp

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

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