smfplay: 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/smfplay - from package: midish

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

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