To do a chirp, you do this: -
1. Start with the fader open.
2. Push the record forward and when you hear the sound start to play, close the fader, but carry on moving the record forwards as if you were doing a baby scratch.
3. Pull the record back as if you were doing a baby scratch, and just before you get back to the beginning of the sample, open the fader again.
The record movement is the same as a baby scratch, except you're closing the fader during the middle part of the record movement so all you hear is the very beginning of the sound, then the very beginning of the sound again - but reversed - as you're pulling the record backwards. That's what gives a nice sharp, defined sound compared to a baby scratch.