Music Maker I

Review — the Geometry Art arc 5 min

• A polygon My Block takes the number of sides as an input.
• The pen turns 360 ÷ sides degrees at every corner.
• Symmetry is one shape, drawn again and again with a turn in between.

Quick-fire

Your polygon block draws a shape with 8 sides. How far does it turn at each corner?

Today’s Topic 3 min

• The Music extension
• play drum [(2) Bass Drum v] for (0.25) beats
• Beats and tempo — set tempo to (60)
• rest for (0.75) beats — a beat of silence

Learning outcome

By the end of this lesson you will be able to:

1. Add the Music extension and play a drum.
2. Say how long a beat lasts at a given tempo.
3. Build a beat that a dancer steps to.

Learnt — drums and the beat 28 min

1 · Add the Music extension

The Music blocks are not in Scratch until you add them.

1. Click the Add Extension button. It is at the very bottom left of the editor.
2. Click Music.
3. A new Music category appears at the bottom of the block list.

2 · Play a drum

1. Add the Drum sprite. Call it Kick.
2. Drag out play drum [(1) Snare Drum v] for (0.25) beats.
3. Click the dropdown and pick (2) Bass Drum.
4. Click the block. You hear one deep “boom”.

Scratch has 18 drums. Each one has a number in the dropdown. These are the four we use in this arc:

3 · Beats, not seconds

Look at the end of the block: beats, not seconds. A beat is one tap of your foot in a song. The tempo says how many beats fit into one minute.

set tempo to (60)
              

set tempo to (120)
              

We keep the tempo in a variable called bpm (“beats per minute”). Then the Stage can show it.

when flag clicked
set [bpm v] to (60)
set tempo to (bpm)
repeat (4)
  switch costume to [drum-b v]
  play drum [(2) Bass Drum v] for (0.25) beats
  switch costume to [drum-a v]
  rest for (0.75) beats
end
set [bpm v] to (120)
set tempo to (bpm)
repeat (4)
  switch costume to [drum-b v]
  play drum [(2) Bass Drum v] for (0.25) beats
  switch costume to [drum-a v]
  rest for (0.75) beats
end
            

4 · Rest — a beat of silence

The drum sound is short, only 0.25 of a beat. The rest for (0.75) beats block fills the rest of the beat with silence. Together they make one whole beat.

5 · Why the drum lights up

Each hit switches the drum to its drum-b costume, then back. Now you can see the beat as well as hear it. It also helps when you are fixing a beat that sounds wrong.

Basic — a beat and a dancer 24 min

Start a new project. Add the Music extension. Pick a dark backdrop, such as Spotlight.

Step 1 — the band

1. Add the Drum sprite and call it Kick.
2. Add the Drum-snare sprite and call it Snare.
3. Add the Ballerina sprite. She is the dancer.
4. Make a variable called bpm, for all sprites.

Step 2 — the kick keeps the beat

1. On the Kick: when flag clicked, then set [bpm v] to (100) and set tempo to (bpm).
2. Add forever. Inside it, put the four lit-drum blocks from the Learnt.
3. After them, add rest for (1) beats. That gap is where the snare goes.

Step 3 — the snare answers

1. In the Kick’s loop, put broadcast [snare v] just before the last rest.
2. On the Snare: when I receive [snare v].
3. Under it: switch to drum-snare-b, play drum (1) Snare Drum for 0.25 beats, switch back to drum-snare-a.

Step 4 — the dancer steps on every beat

1. In the Kick’s loop, add broadcast [beat v] at the start of each beat — twice per loop.
2. On the Ballerina: when I receive [beat v] and next costume.

when flag clicked
set [bpm v] to (100)
set tempo to (bpm)
forever
  broadcast [beat v]
  switch costume to [drum-b v]
  play drum [(2) Bass Drum v] for (0.25) beats
  switch costume to [drum-a v]
  rest for (0.75) beats
  broadcast [beat v]
  broadcast [snare v]
  rest for (1) beats
end

when I receive [snare v]
switch costume to [drum-snare-b v]
play drum [(1) Snare Drum v] for (0.25) beats
switch costume to [drum-snare-a v]

when I receive [beat v]
next costume
            

Faster and faster

Make the drum speed up until nobody could dance to it.

• The first bar of four beats is at tempo 60.
• Every new bar is 30 faster: 60, 90, 120, 150, 180.
• After the bar at 180 it stops and says “Too fast to dance to!”.

when flag clicked
set [bpm v] to (30)
repeat until <(bpm) = (180)>
  change [bpm v] by (30)
  set tempo to (bpm)
  repeat (4)
    switch costume to [drum-b v]
    play drum [(2) Bass Drum v] for (0.25) beats
    switch costume to [drum-a v]
    rest for (0.75) beats
  end
end
say [Too fast to dance to!] for (3) seconds
            

Boom, boom, rest, clap

A rest is part of the rhythm. Use one on purpose.

• Each bar is four beats: kick, kick, a rest, a clap.
• The clap is drum 8, played by the Snare.
• During the rest, the Kick says “rest”.
• Tempo 120, four bars, then stop.

when flag clicked
set [bpm v] to (120)
set tempo to (bpm)
repeat (4)
  switch costume to [drum-b v]
  play drum [(2) Bass Drum v] for (0.25) beats
  switch costume to [drum-a v]
  rest for (0.75) beats
  switch costume to [drum-b v]
  play drum [(2) Bass Drum v] for (0.25) beats
  switch costume to [drum-a v]
  rest for (0.75) beats
  say [rest]
  rest for (1) beats
  say []
  broadcast [clap v]
  rest for (1) beats
end
            

Three drums, three scripts

Each drum plays its own part in its own script. Make them stay together.

• Add the Drum-highhat sprite. It plays drum 6 on every half beat.
• The Kick plays on beats 1 and 3. The Snare plays on beats 2 and 4.
• The Stage sets the tempo to 100, then broadcasts go. All three start on go.
• No drum may use a broadcast from another drum.

when I receive [go v]
repeat (8)
  switch costume to [drum-b v]
  play drum [(2) Bass Drum v] for (0.25) beats
  switch costume to [drum-a v]
  rest for (0.75) beats
  rest for (1) beats
end

when I receive [go v]
repeat (8)
  rest for (1) beats
  switch costume to [drum-snare-b v]
  play drum [(1) Snare Drum v] for (0.25) beats
  switch costume to [drum-snare-a v]
  rest for (0.75) beats
end

when I receive [go v]
repeat (32)
  switch costume to [drum-highhat-b v]
  play drum [(6) Closed Hi-Hat v] for (0.25) beats
  switch costume to [drum-highhat-a v]
  rest for (0.25) beats
end
            

Dance party

Put it all together, and give the player a tempo knob.

• The Ballerina counts in: “1”, “2”, “3”, “4”, one per beat.
• Then the three drums from Challenge 3 play for ever, and she dances on every beat.
• ↑ adds 10 to the tempo and ↓ takes 10 away. It never goes below 60 or above 200.
• The bpm box always shows the tempo you hear.

when flag clicked
set [bpm v] to (100)
set tempo to (bpm)
say [1]
rest for (1) beats
say [2]
rest for (1) beats
say [3]
rest for (1) beats
say [4]
rest for (1) beats
say []
broadcast [go v]

when [up arrow v] key pressed
if <(bpm) < (200)> then
  change [bpm v] by (10)
  set tempo to (bpm)
end
            

Summary 5 min

• Add Extension → Music gives you the Music blocks.
• Music blocks count in beats. The tempo says how long a beat is.
• At tempo 60 a beat is one second; at 120 it is half a second.
• rest for (1) beats is silence that still counts.
• Scripts that count in beats stay together, even in different sprites.

Extension

Extra blocks you add to Scratch, like Pen and Music.

Beat

One tap of your foot in a song.

Tempo

How many beats fit in one minute — the speed of the music.

Rest

A gap of silence, measured in beats.

bpm

“Beats per minute”, our name for the tempo variable.

Hand in

Save your beat. Next lesson the band gets a tune: notes, instruments, and a letter that climbs as the music goes up.