Music Video I

Review — where we got to 5 min

The Muffin Catcher is finished and saved. Two things from it matter today.

• play sound [Pop v] starts a sound and carries straight on.
• play sound [Pop v] until done waits for it to finish.
• Several sprites can run their own loops at the same time, and none waits for another.

Quick-fire

In the Muffin Catcher, “until done” was the wrong block and it froze a falling muffin in mid-air. Today it is the right one. What changed?

Today’s Topic 3 min

• The Sound tab: choosing a sound, and recording one
• forever around play sound [Dance Snare Beat v] until done — a loop with no gap
• A beat of your own: play sound [Drum Bass1 v] then wait (0.5) seconds
• set volume to (100) %, and two sprites playing together

Learning outcome

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

1. Loop a backing track so it plays with no silence between repeats.
2. Build a beat from a sound and a wait, and change its speed with one number.
3. Run two layers at once and keep them in time.

Learnt — loops, beats and layers 27 min

A music video is two jobs. The music, and the moving. They are easier apart, so today is all music and nothing moves at all.

Set the stage

1. Start a new project. Delete the cat.
2. Choose the Concert backdrop.
3. Add the Drum Kit sprite. It is not going to move; it is who the music belongs to.

A backing track is one block in a loop

Pick a sound long enough to be a track. Dance Snare Beat is four seconds and it is built to repeat.

1. Click the Drum Kit, then the Sound tab.
2. Choose a Sound, search Dance Snare Beat, and click it.
3. In Code, build when flag clicked, then a forever.
4. Put play sound [Dance Snare Beat v] until done inside the forever.
5. Press the flag. It should go round with no silence in the join.

when flag clicked
forever
  play sound [Dance Snare Beat v] until done
end
              

when flag clicked
forever
  play sound [Dance Snare Beat v]
end
              

A beat is a hit and a gap

The other way to make music is to hit something on a timer. One short sound, one wait, in a forever.

when flag clicked
forever
  play sound [Drum Bass1 v]
  wait (0.5) seconds
end
            

That number is the speed of your track. 0.5 is a walking beat. 0.25 is twice as fast. 1 is a slow march.

Layers

One sprite, one job. The drum kit holds the beat; a second sprite claps over the top of it. Both start on the flag and neither waits for the other.

when flag clicked
forever
  play sound [Drum Bass1 v]
  wait (0.5) seconds
end
              

when flag clicked
forever
  play sound [Clapping v]
  wait (1) seconds
end
              

Waits of 0.5 and 1 fit together, because one is exactly twice the other. Waits of 0.5 and 0.7 do not, and the two layers drift apart while you listen.

Volume

Every sprite has its own volume. That is how a layer sits under another one instead of fighting it.

when flag clicked
set volume to (60) %
forever
  play sound [Clapping v]
  wait (1) seconds
end
            

Basic — build the track 25 min

Build it in this order, with the volume up, and listen after every step.

Step 1 — the stage

1. New project, cat deleted, Concert backdrop.
2. Add the Drum Kit and the Drums Conga.
3. Put them where a band would stand. They will not move today.

Step 2 — the backing track

1. On the Stage, open its Sound tab and add Dance Snare Beat.
2. Give the Stage the forever-until-done stack.
3. Press the flag and listen for the join. There should be no gap.

Step 3 — the drum

1. On the Drum Kit, add the sound Drum Bass1.
2. Build the hit-and-wait loop with wait (0.5) seconds.
3. Play both together. Tap your foot. Does the drum fit the track?

Step 4 — the clap

1. On the Conga, add Clapping.
2. Build the same shape with wait (1) seconds.
3. Now you have three layers. Listen to the whole thing for twenty seconds.

Step 5 — mix it

1. Give each sprite a set volume to (100) % at the top.
2. Turn the clap down to 60 and the drum down to 80.
3. The backing track should sit underneath, not on top.

Step 6 — change the speed

1. Set the drum wait to 0.25 and the clap to 0.5.
2. Listen. The whole track is twice as fast and still together.
3. Now try 0.3 and 1. Hear them drift apart, then put them back.

Your own two layers

Make a beat nobody else in the room has, out of two sounds and two waits.

• Two sprites, one sound each, both looping.
• The two waits are related — one is double the other.
• You can say which sound is the beat and which is the layer on top.

Thirty seconds, no drift

Anyone can make two sounds fit for three seconds. Make a track that still sounds right after thirty.

• At least three layers running together.
• It plays for thirty seconds without slipping out of time.
• Each layer has its own volume, and you can hear all three.

An intro, then the track

Give your track a proper opening: something that happens once, before the loops start, and never again.

• A count-in, a cymbal, or a spoken line — once only.
• The loops begin after it, not underneath it.
• Running it twice gives the same opening both times.

when flag clicked
set volume to (100) %
play sound [Cymbal Crash v] until done
wait (1) seconds
forever
  play sound [Drum Bass1 v]
  wait (0.5) seconds
end
            

Put your own voice in it

Every sound so far came out of the library. Record one of your own and make it the hook — the bit somebody remembers.

1. Click a sprite, then the Sound tab.
2. Hover the speaker button at the bottom left and choose Record.
3. Press the round button, say your word, press stop.
4. Drag the handles to trim the silence off both ends, then Save.
5. It is now in that sprite’s sound dropdown like any other.

• The hook is a sound you recorded, not a library one.
• It comes round on a timer, not at random.
• It sits over the track without drowning it.
• The trimmed sound has no long silence at either end.

Summary 4 min

Music in Scratch is two shapes, and knowing which is which is the whole lesson.

1. A track: play sound [Dance Snare Beat v] until done inside a forever. No gaps.
2. A beat: play sound [Drum Bass1 v] and wait (0.5) seconds inside a forever. The wait is the speed.
3. Layers are just more sprites doing the same thing, with related waits.

Backing track

A long sound looped with no gap, underneath everything else.

Beat

A short sound repeated on a timer. The wait between hits is its speed.

Layer

One sprite’s loop. Several together make a track.

Volume

How loud one sprite is. Set it at the top of a stack, not once and for ever.

Next lesson: the dancers arrive, and they move on the beat you built today.