midi2abc: 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/midi2abc - from package: abcmidi

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

Error in other languages:
midi2abc: bevel nie gevind nie
midi2abc: comandă negăsită
midi2abc: comando não encontrado
midi2abc: commande introuvable
midi2abc: command not found
midi2abc: käsku ei ole
midi2abc: không tìm thấy lệnh
midi2abc: komanda nerasta
midi2abc: Kommando nicht gefunden.
midi2abc: kommandot finns inte
midi2abc: komut yok
midi2abc: nie znaleziono polecenia
midi2abc: níor aimsíodh an t-ordú
midi2abc: no se encontró la orden
midi2abc: no s'ha trobat l'ordre
midi2abc: opdracht niet gevonden
midi2abc: parancs nem található
midi2abc: perintah tidak ditemukan
midi2abc: príkaz nenájdený
midi2abc: příkaz nenalezen
midi2abc: команда не найдена
midi2abc: командата не е открита
midi2abc: 命令找不到
midi2abc: コマンドが見つかりません