This is a classic scratch done by sucking in air against either a hand or a finger. This is one of the most realistic sounding and effective scratches there is for a beatboxer to do.
How it's done
Fat Tony's Method
- Make a kissy face
- Put your finger against your lip (or, indeed, any part of your hand / arm / foot)
- Inhale whilst breathing words like "too" or "tooka"
- Use uvular oscillation and clickrolls to add rolls to the scratch
- Put into a beat
Note that there are a massive variety of ways you can do this sound. The finger and thumb method described is the most common when it comes to putting the sound into a beat because it's possible to do it whilst holding a microphone. But really, you don't even need to limit yourself to using your hands.
Method 2
- Place the tip of your finger (You can use any finger) just against your mouth.
- It's important to leave the gap in your mouth small (size of a pea) so you can get that whistly sound you want. If you leave the gap bigger you will get a deeper scratch which is still a good sounding scratch but not the one you want.
- Now what you have to do is breathe inwards and you should get that scratching sound.
- Ok now this is the most important part of crab scratching - changing the tones. To change the tones it is like saying "Tooka" but you do it inwards and unvocalized and this should get your crab scratch sounding great.