In the first post, we covered the basic 12 notes which form the musical alphabets. It’s important that you read and understand that first, before continuing on this one. 

The second post covers the science behind each note's different and unique sound. Do check it out if interested, though it’s not a deal-breaker for the rest of the course.



Here are the 12 notes that we learnt previously - 

C  C#  D  D#  E  F  F# G G#  A  A#  B  C







To start, let’s go over the concept of semi-tone -

The distance between two adjacent notes is called a semi-tone. e.g. - C -> C#



So, all these below statements are true - 

• C and C# are one semi-tone apart.
• C# is one semi-tone higher than C.
• D is two semi-tones above C.
• Each note repeats after 12 semi-tones.

We use the terms such as higher or above to represent moving higher on the note/frequency spectrum. On a piano it means moving towards right, and on the guitar it means moving down.



Now that we are familiar with the concept of semi-tone, let’s understand the meaning of interval -

The distance between any two notes is called an interval.



For example, these are all valid intervals - 

• C - D
• C - G
• C - A#
• C - higher C

It takes 2 notes to form an interval. For simplicity, I have taken the note C as the first note, but it can be any other note as well.



You might have guessed that since there are exactly 12 unique notes, there are 12 types of intervals - 

1. Minor Second (m2) - Two notes are just 1 semi-tone apart. ( C -> C# )
2. Major Second (M2)  - Two notes are 2 semi-tones apart. ( C -> D )
3. Minor Third (m3) - Two notes are 3 semi-tones apart. ( C -> D# )
4. Major Third (M3) - Two notes are 4 semi-tones apart. ( C -> E )
5. Perfect Fourth (P4) -Two notes are 5 semi-tones apart. ( C -> F )
6. Tri-tone (TT) - Two notes are 6 semi-tones apart. ( C -> F# )
7. Perfect Fifth (P5) - Two notes are 7 semi-tones apart. ( C -> G )
8. Minor Sixth (m6) - Two notes are 8 semi-tones apart. ( C - G# )
9. Major Sixth (M6) - Two notes are 9 semi-tones apart. ( C - A )
10. Minor Seventh (m7) - Two notes are 10 semi-tones apart. ( C - A# )
11. Major Seventh (M7) - Two notes are 11 semi-tones apart. ( C -> B )
12. Octave (P8) - Two notes are 12 semi-tones apart. ( C -> higher C )

Note : m -> minor, M -> Major, P -> Perfect.

These terms such as minor, major, perfect, octave etc are jargons of music and might seem unfamiliar at first. Though slowly you'll understand the logic behind the naming of these terms.



The above 12 intervals look much clearer in the below pic - 



Among the above 12 intervals, certain intervals sound pleasing, happy or stable to our ears, and are called consonant intervals.

While certain intervals sound unpleasant or unstable and when heard they invoke a feeling to be resolved to a more consonant sound. Such intervals are called dissonant intervals.

Consonant Intervals - Third (Major & Minor), Fourth, Fifth, Sixth (Major & Minor), Octave

Dissonant Intervals - Second (Major & Minor), Tri-tone, Seventh (Major & Minor)



Try out playing these intervals one-by-one on your favorite instrument and see if you notice any difference between the sound of various intervals. This is how I would play it -

On the piano - Press the first key and then the second key to form the interval

On the guitar - Pluck the first note and then the second note to form the interval



That’s it for this one. In the future posts, I will cover the different types of scales and chords. Stay tuned.

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