Sonic is another fundamental trick. It’s not as easy as TA to grasp how it works, but once you know it, it’s easy as hell. The pen rotates between 1 and 3 and goes around 2. When you’re starting out with learning this trick a good tip is to start out with the back of the pen stuck behind your thumb, so you can build up some pressure to give the pen speed. Once you know the trick a good idea is to train this away.
Step 1: Hold the pen with 2 and 3 at the CoP with the rear stuck behind your thumb.
Step 2: While lightly pressing 2 down, release the pen with T and continue pushing 2 down. When releasing the pen with T, push 1 towards 3, so you catch the pen between those fingers.
Step 3: Let the pen make a nice rotation between 1 and 3 untill you can unfold 2 again so the pen ends up between 1 and 2 instead.
Step 4: Catch the pen between 1 and 2 and let it rotate untill you catch it with your thumb.