Hi Sunny,
What you were hearing with the Silver Trumpet demo were trills, not shakes.
These trills are allowed by the switching of the voice to monophonic, enabling the player to hold a key down and press another lower or higher key repeatedly and quickly, resulting in a trill.
The Big Band Trumpet will do shakes with increased velocity.
Ian
_________________________
Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.