musicxml2ly: 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/musicxml2ly - from package: lilypond

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

Error in other languages:
musicxml2ly: bevel nie gevind nie
musicxml2ly: comandă negăsită
musicxml2ly: comando não encontrado
musicxml2ly: commande introuvable
musicxml2ly: command not found
musicxml2ly: käsku ei ole
musicxml2ly: không tìm thấy lệnh
musicxml2ly: komanda nerasta
musicxml2ly: Kommando nicht gefunden.
musicxml2ly: kommandot finns inte
musicxml2ly: komut yok
musicxml2ly: nie znaleziono polecenia
musicxml2ly: níor aimsíodh an t-ordú
musicxml2ly: no se encontró la orden
musicxml2ly: no s'ha trobat l'ordre
musicxml2ly: opdracht niet gevonden
musicxml2ly: parancs nem található
musicxml2ly: perintah tidak ditemukan
musicxml2ly: príkaz nenájdený
musicxml2ly: příkaz nenalezen
musicxml2ly: команда не найдена
musicxml2ly: командата не е открита
musicxml2ly: 命令找不到
musicxml2ly: コマンドが見つかりません