DJ Mathematics Part 1: Scratch History

1973: Kool Herc decides to DJ a party for his sister. He brings in two turntables, and switches from record to record without any pauses. 


1974: DJ Pete Jones introduces a switch so he can control which of two records he is listening to on his head phones, and match the beats between them. Grandmaster Flash does the same but adds sampling techniques.

The mathematics of beat matching has roots in African tradition

It can also be seen in Afro-Caribbean music traditions

1977: Grand Wizard Theodore --at age 13! -- invents the scratch. This happened by accident -- he was just playing with a record while his mom was asking him to turn down the music, and he decided that he liked the sound imposed on the other record that was playing.

Some contemporary examples:

Oscillation of fader: chanfade.wmv

Serato Scratch Live

DJ  Mathematics Part 2: Patterns in time

1) Fader time series waveforms

But  what about other waveforms?

Sawtooth wave



Square wave

2) Turntable time series waveforms

But again, we have to think about other waveforms!