A scale starts with the note that names the key. This note is the tonal center of that key, the note where music in that key feels "at rest". It is also called the tonic, and it's the "do" in "do-re-mi". For example, music in the key of A major almost always ends on an A major chord, the chord built on the note A. It often also begins on that chord, returns to that chord often, and features a melody and a bass line that also return to the note A often enough that listeners will know where the tonal center of the music is, even if they don't realize that they know it. (For more information about the tonic chord and its relationship to other chords in a key, please see Beginning Harmonic Analysis.)
Example 1
If you are having trouble deciding whether a piece is in a major or minor key, try the following steps:
- Find the key signature.
- Determine the major key represented by that key signature, and its relative minor (the minor key that has the same key signature.
- Look at the very end of the piece. Most pieces will end on the tonic chord. In many, the melody will also end on the tonic, but this is not nearly as reliable as looking at the entire chord. If the final chord is the tonic of either the major or minor key for that key signature, you have almost certainly identified the key.
- If the final chord is not the tonic of either the major or the minor key for that key signature, there are two possibilities. One is that the music is not in a major or minor key. Music from other cultures, as well as some jazz, folk, modern, and pre-Baroque European music are based on other modes or scales. (Please see Modes and Ragas and Scales that aren’t Major or Minor for more about this.) If the music sounds at all "exotic" or "unusual", you should suspect that this may be the case.
- If the final chord is not the tonic of either the major or the minor key for that key signature, but you still suspect that it is in a major or minor key (for example, perhaps it has a "repeat and fade" ending which avoids coming to rest on the tonic), you may have to study the harmony in order to discern the key. Most tonal music will feature the tonic and dominant chords of the key. (You will find more about which chords are common in a given key in Harmonic Analysis.)



Interval
Triads






