The free buzz is a practice technique championed by legendary hornist and pedagogue, Julie Landsman. I have incorporated her thoughts and perspective into my own teaching and have developed similar exercises to share with my own students. I find them highly effective in encouraging regular, consistent airflow as well producing a simple, yet powerful sound.
You can find Professor Landsman’s Free Buzz Method here: Carmine Caruso Method
The exercise below is an effective exercise in creating an efficient buzz: