This screen cast will show you how to make your DJ control the frequency of a repeating sound using the scroll bars on the screen.

DJs make short sounds called samples or other musical sounds into their underlying track to create a new song.

As a DJ drags the scroll bar, the sound of the sample speeds up or slows down.

To start, choose a sample sound that you wanna mix into your song.

Ya, ya.

Just like with the musical loop track, you want it to play forever once the flag is clicked.

Go ahead and add the blocks needed to play the sound forever and to start runnin' the code when the flag is clicked.

This block stack probably looks familiar to you.

The starting event block, when flag clicked, will start running this stack when the flag is clicked.

And since there are two of these both the ya sound and the techno sound will start when the flag is clicked.

This example shows a forever loop and the play sound block that will make the ya sound keep playing over and over again once it has started.

Try out your code.

Ya, ya, ya, ya, ya.

That doesn't sound so good, the ya is playing over and over again so quickly, no single ya, ever finishes.

Try adding a wait block to space out the sound.

Usually, the best way to solve a problem like this one is to keep trying blocks and testin' the code until you find the fix that works for your program.

Ya, ya, ya, ya.

That's better, but if you wanna speed up or slow down the ya sound, you can change the one second to any number you want, like four.

That works, but it would be too hard to keep changing that number while the user is mixing in more sounds.

Computer scientists often build tools others will use, so, they need to keep the users of their programs in mind when they build, for example, the computer scientists who built the DJ mixing tools you saw in today's starting screen cast, had to think about making a tool for the DJs that was both powerful and easy to use.

Ya. You want this tool to be as easy to use as possible for future contestants in your battle of the DJs.

It is too hard to change the number to control the speed of the sound and press the space bar to make the sound play at the same time.

In the next screen cast, you'll learn how to make a sliding control to adjust the speed of your repeating sound.

Now it's your turn.

Add a sound that will play repeatedly once the green flag is clicked.

Remember, if you get stuck, you can always ask your neighbor for help.


  1. Choose a new sample sound to mix over the background track.
  2. Program the sample sound to play continuously.
  3. Add a "wait" block to slow down the speed of the sample.