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1. DJ Mixer Intro


Welcome back to CS First Scratch Music and Sound, where you use computer science to make creative projects involving sound. Today, you will make a DJ mixing tool. DJs use scratching techniques and digital mixing boards to build their own music. They incorporate sounds sampled from other songs and mix them into an underlying beat for people to dance to. While watching the dancers, DJs can use the mixing board to adjust their music choices, sample selections, and scratching techniques in the moment to engage their audience. DJs even “battle” at world-wide events, where they are given a limited amount of time (usually anywhere from 30 seconds to a couple of minutes) to show off their skills.

Did you know that the mixing board that makes all of this possible is actually a type of computer that uses technology built by computer scientists? Take a look at some DJs, and notice how they they use technology to create music.

My work always involves technology, and it always involves building my own tools, whether it's in software or hardware.

Today, you'll create a DJ Mixer in Scratch to mix music, change the speed of a repeating loop, and play sampled sounds on a keyboard. Take a look at this example DJ Mixer. A loop of background music starts playing when the flag is clicked. The DJ can use the "meow speed" slider to adjust the frequency of the "meow" sound. Or, pressing the spacebar like this <press spacebar> will play an additional sound.

In today’s club, you’ll build a DJ Mixer tool like this one and choose the sounds to make your own dance track or even DJ battle with your friends.

Here is another example of a DJ Mixer that has a lot more sounds and options for the DJ to use.

To get started, just as you did on your other club days, sign in to Scratch with the information from your CS First club pass, create a new project, delete the Scratch cat, and name your project "DJ Mixer."

Next, choose any sprite you like to be the DJ.

Remember to help your neighbor if they have a question or ask them to help you. When you are finished with these steps, come back to this CS First tab and click the green arrow to move on to the next screencast.

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  1. Sign in to Scratch.
  2. Create a new project and name it "DJ Mixer."
  3. Delete the Scratch Cat and add a new sprite.