abc2ly: 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/abc2ly - from package: lilypond

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

Error in other languages:
abc2ly: bevel nie gevind nie
abc2ly: comandă negăsită
abc2ly: comando não encontrado
abc2ly: commande introuvable
abc2ly: command not found
abc2ly: käsku ei ole
abc2ly: không tìm thấy lệnh
abc2ly: komanda nerasta
abc2ly: Kommando nicht gefunden.
abc2ly: kommandot finns inte
abc2ly: komut yok
abc2ly: nie znaleziono polecenia
abc2ly: níor aimsíodh an t-ordú
abc2ly: no se encontró la orden
abc2ly: no s'ha trobat l'ordre
abc2ly: opdracht niet gevonden
abc2ly: parancs nem található
abc2ly: perintah tidak ditemukan
abc2ly: príkaz nenájdený
abc2ly: příkaz nenalezen
abc2ly: команда не найдена
abc2ly: командата не е открита
abc2ly: 命令找不到
abc2ly: コマンドが見つかりません