xplaymidi: 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/xplaymidi - from package: playmidi

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

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