Keys
A key is a group of pitches that belong together. The group of pitches are exactly the same as the scale notes, which will be explained in more detail in an upcoming lesson, however the term ‘key’ itself is simply used to identify the name of that group of notes in no particular order, through the tonic of the group.
The tonic of the group is the note that is the tonal centre of the notes and although there is a much more scientific reason why it is the tonal center, for all intents and purposes, it is the note that has the strongest pull towards it and that all other notes seem to want to resolve to. In fact, there is a particular interval each other note has to the tonic therefore as the reference note, it is also the ‘key’ note and therefore used to name the group. One example would be : The ‘key’ of C major contains the notes C, D, E, F, G, A and B. Therefore the universe of notes that can be used together that would compliment C as their tonal center are C, D, E, F, G, A and B. The ‘key’ of C major contains all natural notes and no other key is made up of the same notes.
On a piano, this would mean ‘all white keys’ therefore if you were to play a melody using all the white keys of a piano, without touching any black keys (which would be sharps or flats), you would be playing in what is called key of C Major. Resolving your melody on the C note would feel final compared to other notes, although we’ll get into exceptions later.
I don’t exactly know why the term ‘key’ is specifically used to describe this group of notes that belong together or to refer to the tonic, however some things just need to be memorized without a better explanation.
Note that the group of notes belonging to the key are also the notes used to create each of the seven chords that belong to a key. Using any note that is outside of the group means that either an exception has occurred, or an error has been made. More on this later. The ‘sharps’ or ‘flats’ are called ‘accidentals’ by the way. There is no particular reason that I’m aware of as to why they are referred to as ‘accidents’ as ‘accidentals’ are required to create the correct patterns of notes in different keys. If I do ever figure it out, I’ll update the portion of this course to provide that explanation for you.