Certainly sounds like he's trying to crow - they are very "croaky" at first.
But nine months old? What breed is he? My 6-month old roo - a GORGEOUS Amauracuna/Silkie cross - has been crowing for over 2 months and took control of the flock over from his "daddies" several weeks ago.
I had three roosters this summer, one was snatched, he had been crowing for about a week, he was about 31/2- 4 months old..... but what is funny, is that the other two, just started to try and crow now, and they are nearly 6 months old. One is the same breed as the early crower. They are like kids, they grow at different rates!