ym2wav: 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/ym2wav - from package: stymulator

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

Error in other languages:
ym2wav: bevel nie gevind nie
ym2wav: comandă negăsită
ym2wav: comando não encontrado
ym2wav: commande introuvable
ym2wav: command not found
ym2wav: käsku ei ole
ym2wav: không tìm thấy lệnh
ym2wav: komanda nerasta
ym2wav: Kommando nicht gefunden.
ym2wav: kommandot finns inte
ym2wav: komut yok
ym2wav: nie znaleziono polecenia
ym2wav: níor aimsíodh an t-ordú
ym2wav: no se encontró la orden
ym2wav: no s'ha trobat l'ordre
ym2wav: opdracht niet gevonden
ym2wav: parancs nem található
ym2wav: perintah tidak ditemukan
ym2wav: príkaz nenájdený
ym2wav: příkaz nenalezen
ym2wav: команда не найдена
ym2wav: командата не е открита
ym2wav: 命令找不到
ym2wav: コマンドが見つかりません