As you've probably already noticed, notes are named after the letters of the alphabet, A - B - C - D - E - F - G. You've probably also noticed we have way more than seven notes so how do we make these letters work for all the different notes? We will go into more detail later, but for now all you need to know is we can raise a note by a half step with a sharp (#) or lower it the same amount with a flat (b). Also, if you take the rate a note vibrates (say, 440 times a second for an "A") and double it, you get the same note an octave higher (880 times a second) or if you cut it in half, an octave lower (220 times a second). This is how a piano winds up with 88 keys - each octave has another set of the same notes, only lower or higher.