What purpose do accidentals serve in music?

Question

I'm having trouble writing music containing accidentals.If the diatonic scale contains 7 related notes, what purpose do accidentals serve? If the accidental notes are not related to the overall scale, how can they ever sound good?Very often when I use an accidental in composing, even if it's part of a chord, it sounds "wrong" to me. How do I know when to use them, and how do I use them correctly?

Answer 1

Instead of "accidental notes" you mean to say "non-diatonic notes", meaning notes that are not native to the key you are in. These will usually be indicated by using accidentals: sharps, flats or natural signs. Non-diatonic notes occur for different reasons. You could have a chromatic passing tone in a melody, for example: C, C#, D. Or, you could have a temporary non-diatonic harmonization, for example a D major chord in the key of C major would require the introduction of an F#. Find a few pieces of printed music and study them, you will find examples. Find music in the key of C and scan the score visually for any sharps or flats. Then listen to what is happening in those moments. This should help you more than anything to understand the function of non-diatonic notes.

Answer 2

Imagine a melody in the key of C, no accidentals exist in the key signature. How might you harmonize the melody, E-D-C ? You question seems to constrict us to:

G,C to compliment the E as a C triad;

F,B to compliment the D as a rootless G7;

E,G to compliment the C as C triad.

Suppose we harmize the D with F,Ab, instead? Does this sound wrong to you?