When you play music with other people, you have to be able to talk about what you're going to play. To do that, you have to know how to speak the language. Learning the music alphabet will help you do that.
Notice: You don't have to read music for this!
The language of music is just like any other language. That's why we use the music alphabet. It's a simple system of letters that help us write down the sounds we actually want to play.
All music is made up of notes. A note is just any pitch made by a musical instrument. Every note in music has a letter name. The music alphabet is made up of only seven letters: A-G. This is because when we play the notes in order, the note that we would call "H", sounds like another "A", so we just start the set over. Example:
A B C D E F G A
C D E F G A B C
This is similar to counting numbers. You start with 1, then 2, 3 and so on, but when you get past 9, you don't start making up new numbers, you start back with 0, with a 1 in front. Then the same thing happens with 20 and 30 and so on.
In music, we call these sets octaves. So when you get to the next highest note with the same letter name, it will still be an "A" note, but it's pitch will be in a higher octave.
The image above shows how the notes continue in both directions, (hence the "..." on both ends). When you are going to the right, or up the alphabet, you don't stop at G. Instead you start over at the next highest A and keep going.
The same thing happens for the opposite direction as well. When you are going to the left, or down the alphabet, you don't stop at A. You simply start over at the next lowest G and keep going.
Even though the music alphabet is only made up of 7 letters, that doesn't mean that there are only seven notes. There are actually 12. The seven letters represent natural notes. Don't get hung up on this word. Natural just means they are regular notes, they are just the regular alphabet letter name like A, C, or G.
The other five notes fall in between these letters in the form of sharp notes or flat notes. We write these sharp notes and flat notes by adding either a sharp symbol ♯, or a flat symbol ♭ to the natural notes.
A sharp note is one note higher in pitch than the natural letter it uses. (So A♯ is higher than A.) A flat note is one note lower in pitch than the natural letter it uses. (So A♭ is lower than A.)
NOTE: Going to the right on this line would be going higher in pitch (or going "up"), and going to the left would be going lower in pitch (or going "down").
Here is how this would work out on a piano keyboard. The blue notes are natural, the red notes are sharp, and the orange notes are flat.
(Click for larger image)
You might notice that certain sharps or flats take up the same space on the keyboard. That's because they are actually the same note, they are just called by a different name depending on the where we use them. We call these kinds of notes enharmonics. That means that A♯ and B♭ are the same note, C♯ and D♭ are the same note, and so on.
You may also notice that there are no sharps or flats between B-C and E-F. Now that doesn't mean there is no such thing as a B♯ and F♭, we just usually call them by C and E.
"Sharp" and "flat" can also be verbs. When we sharp a note, we raise its pitch by one note. When we flat a note, we lower its pitch by one note.
So when we sharp a D, we get D♯. When we sharp a B, we get a C. Also, when we flat a B, we get B♭. When we flat an F, we get E.
Notice: Don't worry about why there is no note between B-C or E-F. It is best just to accept that this is how it is and learn it this way. To question this would be like questioning why you never see Q without a U beside it in any words in the English language. While there probably is a reason for it, it has nothing to do with playing music, so let's not waste time on it.
note - a pitch produced by a musical instrument. (Also a mark written on a page to represent such a pitch.)
octave - a range of notes from one letter name up to the next highest (or down to the next lowest) pitches by the same letter name.
natural notes - notes represented by the seven letters of the music alphabet with no sharp or flat symbols.
sharp notes - notes represented by any letter of the music alphabet with the sharp symbol (♯) added.
flat notes - notes represented by any letter of the music alphabet with the flat symbol (♭) added.
enharmonics - two notes with the same pitch, only called by a different name. (A♭ and G♯)