Musical instruments make different sounds, or pitches, mostly because of something called frequency.

Frequency is about how many times a sound wave goes up and down every second. You can think of a pitch like a musical note. The frequency decides if that note sounds high or low.

Here’s the simple rule:

• Higher frequencies make higher pitches.
• Lower frequencies make lower pitches.

What is Frequency?

Frequency is measured in hertz (Hz). This tells us how many times a sound wave goes up and down in one second.

For example, if a sound wave has a frequency of 440 Hz, it means it vibrates 440 times in one second. This specific frequency is linked to the musical note A, above middle C.

Many musicians use this note to tune their instruments.

How Do Instruments Make Different Frequencies?

Different musical instruments create sounds in special ways. Here’s how some of them work:

1. String Instruments: Think of instruments like violins and guitars. When you pluck a string, it shakes. The length, tension, and thickness of the string change the sound’s frequency.

   • A shorter, tighter string vibrates faster, making a higher pitch.

   • A longer, looser string vibrates slower, making a lower pitch.

   • Key Points:

     • Shorter strings = higher pitch
     • Longer strings = lower pitch
     • Tighter strings = higher pitch
     • Looser strings = lower pitch

2. Woodwind Instruments: Instruments like flutes and clarinets work by moving air. When you blow into them, it creates a vibration inside the tube. The length of the air column is important. Pressing keys opens or closes holes, changing how long the air column is.

   • Key Points:
     • Shorter air columns = higher pitch
     • Longer air columns = lower pitch

3. Brass Instruments: These include trumpets and trombones. They make sound when the player’s lips vibrate against the mouthpiece. The length of the tubing and how you adjust it changes the sound.

   • Key Points:
     • Adjusting length (like with slides or valves) changes pitch
     • Lip tension can also change pitch

4. Percussion Instruments: Instruments like drums and xylophones make sound when their surfaces vibrate. The pitch depends on the size of the instrument and how tight they are. For example, hitting a bigger drum makes a lower pitch than hitting a smaller drum.

   • Key Points:
     • Larger drums = lower pitch
     • Tighter drum heads = higher pitch

Musical Scale and Pitch

In music, the musical scale is divided into 12 equal parts, called semitones, in each octave.

When you increase the frequency by a certain amount, you create a different pitch. For instance, if you double the frequency, the sound goes up one octave, which is a higher pitch.

This idea can be shown with a formula:

$$f_2 = 2 \cdot f_1$$

Here, $f_2$ is the frequency that is one octave higher than $f_1$. This relationship helps musicians create sounds and melodies that are nice to listen to.

In short, the different pitches we hear from instruments come from how they vibrate and their unique features. By understanding frequency, we can see how the wonderful world of music is made!