Making Music

In this lesson, we are going to start programming in Scratch in ernest. Most of the blocks will be from the Sound palette, as we will be making music.

To begin, start a new project and delete the default sprite that is automatically added to every new project. You can do this by either selecting the Scissors tool (in the toolbar), or right-clicking on its image in the Sprite Container (the panel in the bottom right-hand corner) and selecting delete from the pop-up menu.

Now, either import or draw the following picture:

This octopus has a number of drumsticks, and this gives me an idea. What if we made a project full of drums, and clicking each drum would make a different sound. Sounds fun?

Changing Sprite Names

I would encourage you to keep your project clean and readable, and having a sprite named Sprite1 doesn't help. You will notice that a sprite's name is in the Sprite Information area (the panel in the center below the menu buttons). If you click on the name, it becomes highlighted in blue. At this point, type in the sprite's new name, Octopus.

Playing a Drum

Now that the house-keeping is done, let's make some noise. The octopus is holding a triangle, and that would make a good first instrument. With the Sound block group selected, drag out the play drum block.
Plays a particular drum instrument for a given number of beats. The drums are listed by their number, but clicking the arrow reveals their names. Beats can be in parts of a beat by using decimals, e.g. 0.5 for ½



Begins a block stack whenever the sprite is clicked on the stage. You can have multiple instances of this block, and when a sprite is clicked, all attached block stacks are executed.

It has two values, the first is the type of drum to play, and the second is how long to play it (in beats). Select (81) Open Triangle by clicking on the black down-arrow icon. Note: Depending on the size of the Scratch window, you may have to select the more.. item at the end of the list before you will see the Open Triangle. Clicking more at the end of the list will start the drum list again.

Once the drum instrument is selected, its number appears in the play drum block, not the instrument's name. While it saves on screen space, this aspect can be annoying.

The play drum block defaults to playing for a fifth of a beat (0.2). Let's have the sound last a little longer, so change that to ½ beat by clicking and typing, 0.5 in the second field. Double click on the play drum block in order to hear a triangle sound.

Note: Changing the beat actually doesn't affect the sound of the drum. It still plays the full drum sound whether the value for beats is 0 or 100. We specify a particular value when we play a series of drums and want to play them with a particular tempo. I'll explain that in detail later in the lesson.

Clicking a Sprite

We want the triangle to chime when the octopus is clicked, and this means that we will trigger our play drum script using a Hat Block. Under the Control block group, you will notice a block labeled, when Octopus clicked. Drag that over and connect it above our play drum block.

Instead of double-clicking on our block stack, click on the octopus on the stage, and you'll hear the triangle chime. Yes, I'll answer a couple of questions.

Can you have more than one when sprite clicked hat blocks for one sprite?
Yes, you can. What happens when you click on the sprite is that all of the attached block stacks get executed at the same time.

Well, not exactly at the same time, but essentially at the same time. Let's have an experiment. Duplicate the stack block and change the drum instrument and try it out. You'll notice that both drums are played almost at the same time, but if you pay close attention, you'll notice that one will start slightly ahead of the other. Oh, and it is arbitrary which will start first. I'll tell you why at the end of this lesson.

Let me anticipate your other question. Yes, changing the name of the sprite automatically changes the name of the when sprite clicked block. But you can see when I begin, why I set the name of a sprite to something meaningful.

You may notice that you can't click the octopus image too quickly, for a double-click doesn't trigger our block stack twice, but simply selects the sprite. If you want to wail on that triangle, enter Presentation Mode by clicking on the Enter Presentation Mode icon.

In this mode, you are only running your project, not developing it, so you can click on the octopus as fast as you want. Your project is also displayed at twice the resolution, so it appears much bigger (with the expected resolution loss). Click the Return Arrow in the top-left corner to go back to developing your project.

Rotating a Sprite

All we need to do to finish this project is import some drum instruments, however let me show you some tricks to make that part easier.

First, import a drum. You will notice that Scratch comes with two drum images in the Things directory folder. After importing it, you can drag it on the stage to position it correctly. However, it may not have the correct angle. You can rotate a sprite in the Sprite Information area:

You will notice the reduced version of the sprite's current costume with a horizontal blue line. This line is a handle that shows the sprite's rotation value and can be used to change that value. Change it by clicking and dragging it around. You will notice that the sprite on the stage will rotate around its center.

Duplicating Scripts to Another Sprite

The script that the octopus and the drum use are very similar, so let's copy the octopus' script to the drum.

To do this, click on our Octopus sprite in the Sprite Container panel and view its script. Now click on the Stamp Tool (or Duplicate Tool) in the toolbar and drag the script down to the drum sprite in the Sprite Container panel. Don't let go of the mouse button until the drum sprite is outlined (see below):

After making a copy of the script for the drum sprite, the tool reverts back automatically to the Select Tool (the Arrow), which allows you to click on the drum sprite in the Sprite Container to see the results.

Note that the when Octopus clicked block has automatically changed to when Snare clicked (or whatever you named your drum sprite). However, the drum instrument is still the same. Change this to a snare drum or another drum instrument.

Feel free to take a minute to make your own drum set. I've provided some additional drum instruments on my web site to help you get started. Hrm, I really should make a vibraslap††Because a cuica looks just like a drum from the outside.

Rhythm Involves Resting

After making and playing with your new drum set, you may realize something: you have no rhythm. Actually, you may have rhythm, but it is hard to keep a good beat going with a mouse, so let's have Scratch keep the beat and allow us to riff on top.

With this, let's associate the rhythm with the stage. That's right, the stage can have scripts as well as sprites. Click on the stage and make sure its Scripts tab is selected.

Remember what I said earlier about the amount of a beat for a drum? Now is the time to put that into practice. We can use the play drum and the rest for blocks
This block does nothing for a given number of beats. The amount of time this actually takes depends on the tempo set for this sprite. Only useful with the play drum and play note blocks. in order to make a drum lick. Try this standard:

Repeating a Stack

The first thing we need to fix is make our rhythm repeat, for it does no good to have a lick play once. Let's use the forever crocodile block (we call it that because the block looks like a reptilian orifice– er, crocodile's mouth).
Repeatedly runs whatever blocks are inside until the Stop sign is clicked or the stop all scripts block is executed.

Note that when you drag the forever block from the Control group panel and position it near the start of our stack, the mouth enlarges to encompass the rest of the stack, for that shows you just what will get inserted into its gaping maw.

Your stack should look something like this:

Double click our stack and the beats goes on and on and on. Click the stop sign icon at the top right to give yourself a rest, for that icon stops all scripts running in all sprites (and the stage too).

Setting the Tempo

I used a ½ beat (0.5) because it is easy to add all the beats to make a measure. However, it sure is slow. Doesn't sound at all like it does when I get on a drum set. We can set the tempo using the set tempo to block,
Specifies the speed, or number of beats per minute, the drums and the notes will be played. 60 bpm means each beat lasts 1 second.

Makes a drum sequence or melody speed up with a positive number or slow down with a negative number.


Starts running the stack attached to it when the green Start Flag icon, or when the project is initially started on the web site. You can have many instances of this block, and all stack blocks would be executed. and attach it to the beginning of our drum lick stack.

You can play around with various values, but I find that 180 bpm (beats per minute) sounds right.

Starting Scripts Automatically

Double-clicking a stack is fine when your developing your project, but we should start our background rhythm automatically. We use the green Start flag icon (top right corner) for officially starting our project. In the Control group, drag the first block to the top of our stack:

Clicking on the Start Flag icon begins our rhythm allowing us to click the other sprites in our drum set.

Multiple Instruments

I think our drum lick should be riding the hi-hat– I mean, we should have a high-hat hit at the start of each beat. However, we are already hitting a drum at that same time.

To get around this problem, we will have two drum stacks: one for the snare and bass drum and another for the hi-hat. Each will get kicked off with the Start Flag icon:

If you play our project long enough, you'll notice something disconcerting: the hi-hat can get out of sync with the drums. Why? Well, I'll discuss this in the Software Engineering Concepts near the end of the lesson.

Make Some Music

Let's leave the drums and work on making a melody. Save and start a new project, and once again, delete the default sprite as we will be doing all our work on the stage.

For this project, we are going to make a tune, and then use the melody we make to create a musical round where the same tune is repeated by a second voice slightly later. So let's use everybody's favorite round, Row, Row, Row your Boat. Begin by dragging out the play note block:
Plays a note for a given beat duration. The instrument used can be set beforehand with the set instrument block.

By default, it plays 'middle C' (#60), and for Row, row, the first note is an 'E'. Click on the black down-arrow to reveal a keyboard that allows you to pick the correct note:

Once you select the correct note, the block displays the note number (in this case, it is 65). Until you get used to what notes match with numbers, debugging a tune is a little difficult, so play the tune regularly.

Setting the Musical Instrument

Now that we have the basic melody, let's play around with it the way we did at camp when we were kids: we turn it into a round. First, let's repeat our melody three times, up the tempo to 320 bpm and start the music with the Start Flag icon. Oh, and let's change the instrument we use to play the melody using the set instrument to block.
Sets the instrument used for the play note block. There is one musical instrument setting per sprite, so if you want to have more than one instrument playing, they need to come from different sprites.

Clicking the black down-arrow on the set instrument to block shows a list of musical instruments we can use to play our melody:

Each sprite (and the stage as well) can have a single musical instrument setting, so we typically set this once before the tune plays.

The top part of your stack should now include all the preliminary setup code and look like:

In the interest of saving space, I'm only showing you the top and the bottom of the code, as all the notes are the same as above.

Building the Round

A musical round requires multiple voices, but each voice comes in slightly later– in our case, 12 beats later. So use the Stamp/Duplicate Tool and make a copy of our current stack, but replace things like the tempo and instument with a rest of 12 beats.

If you really want to annoy yourself, duplicate that stack, but change the rest to 24 beats. And you wonder why we only did this round once at camp before the councilors would send us to bed.

Setting the Volume

Most applications, like most rock bands, play as loud as they can, and let the user adjust the volume on their speaker system. However, let's be kind to the people next to us and set the volume a bit softer with the set volume to block.
Sets the volume of the drums and musical notes this sprite is producing. A value of 0 or less will make the sprite silent.


Alters the current volume from its current setting. Negative values make the volume softer and positive number make the volume louder. If the new volume ends up less than 0, the music will be silent. Values over 100 become 100.

An interesting idea may be to change the volume softer with each round. In fact, we can make the music softer and faster as the song progresses– which may just save our sanity. Just remember to include a set volume to block at the beginning, otherwise the next time you play your music, you may not hear anything at all.

You can finish by drawing a nice picture of a rowboat going off a water fall or even moving the round sections to different sprites with different musical instruments.

Summary

In this lesson, we covered the basics of making music in Scratch, and showed that simple melodies are best and that harmonies are beyond Scratch's ability. However, this is sufficient for most students, who only think about the melody anyway.

We used drum beats to also discuss repeating blocks and starting and stopping block stacks: the basics of computer programming.

In the next lesson, we will learn various techniques for getting a sprite to move around on stage and the basics of computer animation.

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