Horn Concerto Number Four by Wolfgang Amadeus Mozart
FRAN SCOTT: I love the sound of brass instrumentslike these trumpets trombones and of course horns.
GREG FOOT: Me too. Now this music is calledHorn Concerto Number Four by Mozart. Do you think it might be twiceas good as his Concerto Number Two?
I don't know but I do thinkwe should probably find out how brass instruments work.
Oh…
HE PUFFS
NO SOUND
"Yeah so do I!
LOUD LOW NOTE
Brass instrumentslike this trumpet make sounds when the air inside themis made to vibrate. Vibrating air molecules bumpinto the molecules next to them which makes them vibrate too. This creates a sound wave whichtravels through the instrument and comes out of this part which is called the bell. When a sound wave reachesour ears we hear the sound. We can imagine whatthose sound waves look like using this spring so Greg catch one end.
FRAN: Nice! And if we imagine that the brassinstrument is at this end then as that sets the air vibrating it starts off the sound wave like this. It's good isn't it?"
"Oh yes wicked! Look at that."
And you can see thevibration travelling all the way along the spring.Chuck it back. But how do you get the air inthe brass instrument to vibrate? It's not as simpleas just blowing into it… this time.
HE PUFFS
NO SOUND
I still can't do it!
When you playa brass instrument properly this is what your lips look like. In super-slo-mo you can seethat your lips have to vibrate which means they're moving backwardsand forwards really quickly. Believe it or not a player's lips can vibrate over1000 times a second. It's the player's lipsvibrating against the mouthpiece that makes the airin the trumpet vibrate and this creates the sound waves. But these sound waves don't comedirectly out of the bell. Instead they're bouncedbackwards and forwards creating what we calla standing wave.
Let me show you.Right we've got a rope here. "Greg can you…? That end brilliant. Hold it." Now what's going to happen is Greg is going towiggle his end of the rope. It's going to bounce off me andwe should create a standing wave. So go on start your wiggling."Go on go on go on." And there we have it! That is a standing wave and it's known as a standing wave because the wavedoes't look to be moving even though we ARE wigglingthe rope.
Can I stop yet…?!
"Yes you can."
Thanks! Ohh… So what happens is the air insidethe instrument is vibrating. That then sets the air outsidethe instrument vibrating and the vibrations then move throughthe air until they reach our ears.
SHE PLAYS LOUDLY
"It is isn't it?"
"Yeah that's pretty loud!"
"And it is loud"
"Yeah loud because how loud something is its volume depends on the size of the vibrationsthat make up the sound waves. So if I blow hard with more energy I make bigger vibrations."
No…
VERY LOUD NOTE
HE SCREAMS
And that produces a louder sound. If I can make my lips vibratemore gently I make smaller vibrationswith less energy so the sound is softer like this.
SOFTER NOTES
Thought you might.
Yeah I prefer that.
The earliest brass instruments weren't in fact made from brass at all. They were madefrom shells and animal horns which is how some of themgot their name - horns.
Makes sense.
Now modern brass instruments like this French horn look a little bit different. Now one thing you might nothave noticed at first glance is they are just really long tubes. They're just curled upreally tightly to make themeasier to hold and to play. Now if we were to unwind allthe tubing in the French horn you'd find that it's a whopping… five metres long!
LOW SOUND
A sound is coming out but the thing is a major problem is that's very difficult to play lots of different notes. What sort of note comes outof your brass instrument depends how much air insidethe instrument is vibrating. When lots of air vibrates it tends to vibrate more slowly making a lower note. Less air vibrates fasterand we hear a higher-pitched note. Now to prove this I've put three metal tubes inside these three bottlesof coloured water. In this bottle there's a lot of water. In this one not so much and in this one even less. This means there's more airin this tube less air in this oneand even less in this third one. So if I blow across the tubewith the most air in it this one I should make the low note.
LOW NOTE
But if I blow across the tubewith the least air in it this one I should get a higher note. Should!
HIGHER NOTE
And if I blow acrossthe middle tube I should get a notethat's somewhere between the two.
MIDDLE—PITCH NOTE
It worked!
It does work! But the trick is to be ableto quickly change the amount of air that's vibrating in your instrument. There are several waysto do that on brass instruments. Now one way is to usesomething called a slide and this is how a trombone works. If I stretch the slide outas far as I can it makes the tube of air longer and that means a lower-pitched note.
LOUD LOW NOTE
But if I pull it backas far as it will go then the tube of air gets shorter which gives a higher-pitched note.
LOUD HIGH-PITCHED NOTE
See?
Lovely yes.
Now different positions on the slide make different lengths of air which make lots of different notes.
SHE PLAYS TUNE
OK I get it I get it!
Another way of changing the amountof air that's vibrating is to use something called a valve. On an instrument like the trumpet the player can press three valves. This is how you play the note C. And to make a higher note like D you do this. Pressing the valvesmeans there's less air vibrating and that makes the note higher.
Brilliant!
Another brass instrumentis called a bugle and it has no valves at all. And you can make one fromsome ordinary plastic piping so while I finish this off Greg what else have youfound out about brass instruments?
Well they're not ALL made of brass. The shofar is a Jewish instrumentmade from the horn of a sheep. It dates back thousands of years and is still used insynagogues all over the world. How's your bugle getting on Fran?
I'm almost there and this is what you do. You take a length of really cleanhosepipe about a metre long and you've got to wind itround twice like this. And I've used sticky tapejust to hold it in place and stop it from unwinding. Then again we usea clean hosepipe connector and we attach that onto one end and this is going to bethe mouthpiece of our bugle. You need to screw that into placelike that.
Gotcha!
And at the other end you use a funnel. And that is the bell. Easy.
Yeah and then you're all done. It's a bugle.
STEADY LOW NOTE
That's surprisingly good!
"It' good isn't it?" And I've built you one so wecan take our place in the orchestra and jam along with Mozart's Horn Concerto Number Four.
Love to.
Horn Concerto Number Four by Wolfgang Amadeus Mozart
THEY TOOT ALONG WITH CONCERTO
Video summary
In the House of Sound where the science of music and musical instruments is always being investigated, Greg Foot and Fran Scott investigate brass instruments and how they make their loud, bright sounds.
They explain that in order to make a sound, a brass player's lips must be made to vibrate very, very quickly. When placed against the mouthpiece of the instrument the air inside begins to vibrate too, forming sound waves.
To make different notes the amount of air vibrating inside the instrument has to be changed.
On a trombone, a part called the slide makes the tube of air that vibrates longer or shorter, and this changes the pitch of the note from lower to higher.
On an instrument like a trumpet, three parts called valves can be pressed down to change the amount of air.
Fran and Greg demonstrate how a sound wave travels using a large metal spring and form a standing wave with a length of rope.
Fran also demonstrates how you can easily make a simple horn from a funnel, length of hose pipe and a hosepipe connector for a mouthpiece.
This clip is from the series House of Sound.
Teacher Notes
Pupils can experiment with making sounds using just their own bodies and voices. Because sound needs a medium to travel through, they can discuss the media with which they are familiar - for example, water, a highly effective medium, as they may have discovered while swimming.
As an introduction to pitch, experiment with rulers on the edge of desks or tables, so they can find out and record that a long length of ruler vibrates more slowly than a short length and makes a lower sound.
This clip will be relevant for teaching Science or Music in primary schools at Key Stage Two or Second Level (Scotland).
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