Circuit Playground Musical Glove

There are lots of options for writing simple "synth" programs using MakeCode! Here's an example that uses the on tilt Input blocks. When you tilt the CPX, it triggers an event that plays notes which go up or down, faster or slower. The button below will open the program in MakeCode so you can test it and play around with it. Then read the instructions to see how it was put together.

Click here for the Simple Tilt MakeCode program!

Translating Pitch Into Frequency

When you control musical sounds with movement, you are changing the numbers that represent those sounds: the pitch, the tempo, the duration, and the volume. To change the pitch, you need to replace the names of the notes with their numbers.

As you already saw, every note on the drop-down piano keyboard on a play tone shows a number when you press it. This is the frequency of that note. It measures how often a sound wave at that pitch vibrates in one second, and is given in hertz (written Hz).

Middle C has a frequency of 262 Hz. Middle A, five notes higher on the piano keyboard, has a frequency of 440. By using numbers instead of names, the CPX can play a much wider range of frequencies than the keys on the piano keyboard, including tones between standard notes.

Changing Pitch Using Variables

MakeCode includes a change tempo to block that lets you adjust the tempo while the program is running.

But to do the same with the pitch, you need a couple extra steps. First, you'll replace the number with a variable. Then you can change the variable to change the number.

You can also create variables to replace the numbers in volume blocks or the number of beats in a note.

	Create a Variable for the Pitch Click on the VARIABLES category to open up a box that lets you give the variable a name. Let's call this "Note." The VARIABLES menu now contains blocks with the name Note. To set the value of Note when you begin the program, take an `on start` block from the LOOPS menu and drag a `set Note to 0` block inside it. Type in whatever frequency you like. In this example, Note starts out as `175`, which is Low F on the piano keyboard. Use the `on start` block to set the beginning values of the volume and tempo too.
	Use the Tilt Blocks to Create Notes Grab a `play tone at` block from the MUSIC menu. Then grab a `Note` oval from the VARIABLES Menu. Drag the `Note` oval right over the `Middle C` space and let it snap into place. Go to the INPUT Menu and drag an `on shake` block into the workspace. Click on it to open the drop-down menu and choose `tilt left`. Insert the `play tone at Note for 1/2 beat` block inside the `on tilt left` block. Then get a `change Note by 1 block` from the VARIABLE menu and add it underneath. Change the number to `30`. Test the code on the simulator. Every time you tilt the board to the left, it should play a note that's a little higher than the last one. (The notes may sound sharp or flat because they are not exactly 30 Hz apart.) To play a string of notes going up, grab a `repeat 4 times` block from the LOOPS menu and insert it around the `Note` blocks. You can change the number of times the loop repeats. It's handy to add some lights to show which way the board is tilted. From the LIGHT menu, add a `show ring` block to the stack. Make the lights on the left any color you like by clicking on the color wheel in the center and then on the lights. Turn off the lights on the right by clicking on the grey center and then the lights. At the very end of the stack, add a `clear` block from the LIGHT menu. This turns off all the lights after the code has run.
	Add Code for Tilt Right, Up, and Down Right click on the top of the `on tilt left` stack and choose Duplicate from the list of actions. Then change the input block for the new stack to `on tilt right`. On the `show ring` block, make the lights on the right a new color and blank out the lights on the left. Then replace the number in the `change Note by` block to -30. Now, when you tilt the board to the right, it will play a string of notes that get lower. Add INPUT blocks for tilt down and tilt up the same way, but instead of changing the pitch, use the `change tempo by` block to make the tempo go up or down.