tilt_synthesis: 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/tilt_synthesis - from package: speech-tools

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

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