grepmidi: 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/grepmidi - from package: muse

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

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