Is a minor second half a semitone from the first note, or is it the actual second note played on the scale? For example, in a C minor scale, the starting note is C, and D is the second note one plays; however, if we say a semitone higher then it becomes D#. So what is the correct definition in terms of intervals is the second interval in a minor scale?
**Intervals have two parts to them. One part is how many semitones there are between the two notes in question, the other is what note names they have been given.
That sounds a little strange to most, on first being told, but it's a necessity. Scales have little or nothing to do with naming intervals. But read on...
Your minor second: C>D is a major second. Minor seconds are smaller, by one semitone. By moving D away from C, making D♯, you're actually increasing the interval, to an augmented second. To move that D closer to C, will produce the minor second, thus it's now D♭. C>D♭ is m2.
Do not get fooled by major and minor intervals!! They relate very badly to major and minor scales. And don't try to use scale notes specifically to name intervals.
Always use the lower note as a pretend tonic scale note, but using alphabet note names only. Sounds weird, but it's more simple that way.
And, since you mention D♯, the real name in key C minor (as in question) would be E♭ - and that would make C>E♭ a minor third (m3) - which coincidentally is the third note in the minor scale, after the tonic. Consequently, C>D♯ is augmented 2nd, while C>E♭ (same sounding note!) is minor 3rd. Confusing? Very!
Within scales, we refer to scale degrees. So in C minor, the "second scale degree" is D. The "third scale degree" is Eb.
Semitone or half-step are synonyms. They both mean the distance from one pitch to its immediate neighbor pitch. C to Db; Db to D; D to D#; D to Eb — all are semitones (or "half steps").
Whole steps are the combination of two half steps. C to D; C# to D#; D to E — all are whole steps.
A minor second is a half step in which the letter names of the two notes are adjacent. C to Db is a minor second, and Db to Ebb is a minor second, but C to C# and Db to D are not minor seconds, because they include the same letter name. In other words, the term "minor second" is a half step with a specific spelling.
A major second is a whole step in which the letter names of the two notes are adjacent. C to D is a major second; D to E is a major second; E to F# is a major second.
The terms "minor second" and "major second" are measures of distance between two notes; they do not relate directly to scale position. In a C minor scale, the first two notes (C and D) are a major second apart. The second and third notes (D and Eb) are a minor second apart. One can also say that C and D are a whole step apart, and D and Eb are a half step or semitone apart.
...in a C minor scale, the starting note is C, and D is the second note one plays; however, if we say a semitone higher then it becomes D#
This is correct. But for some technical points,
D is the second scale degree which is not an interval name. The interval name is a major second, and by the more general terms of steps/tones it is a wholestep or wholetone.
D# you could refer to it by scale degree. It's still a type of
D so it is a form of the second scale degree, but it it raised a halfstep. You could call it a raised second scale degree. In this scale degree context "raised" or "lowered" is understood to be by halfstep. However, a raised second scale degree is odd. More likely in would be enharmonically spelled as
Eb, a lowered third scale degree, or given we are in
C minor it's just the diatonic third scale degree. In terms of intervals
D is always a second of some type regardless of key signature or accidentals.
D# with the raised second degree would technically be an augmented second, and the enharmonic
Eb would be a minor third.
...So what is the correct definition in terms of intervals is the second interval in a minor scale?
Well, again in terms of proper interval names
D# is an augmented second. But, the question of "what scale?" gets a bit tricky. You already said the scale was
C minor, so the scale is
C minor, and the
D# might be either a moment of some chromatic harmony, or possibly an enharmonic spelling error for
Eb. You would need a little more harmonic context to say one way or the other.
I will go out on a limb and assume your question is more generally about any chromatic tone amongst diatonic scale tones. So, if we have diatonic
CDEFGABC, the chromatic tones are the
A#/Bb. You can generally say those tones will come from three sources:
- borrowing the minor third, sixth, or seventh from the parallel minor key (in minor keys there is also "borrowing" of the lowered second degree from phrygian mode)
- raising tones to create temporary leading tones
- lowering tones to create temporary subdominant tones
As far as the internal names is concerned it does not matter what the key or scale is, you only need to know the "spelling" of the two tones. So, for example,
F# is always a major third, regardless whether it's played in
C minor, or any other key.
If the question is genuinely confusion about whether
Eb is the right diatonic spelling in
C minor, you need to learn the key signatures.
C minor is three flats, and spelled
C D Eb F G Ab Bb C. No sharps. And we will skip the complexity of natural/harmonic/melodic minor scales. That another topic.
I'll answer with a slightly different approach than the previous two chaps:
When discussing intervals, the modifiers "major" and "minor" absolutely relate to major and minor scales. But there are some caveats.
For several intervals, if they are called "major," they appear in the major scale; if they are called "minor," they appear in the natural minor scale. (Because there are other forms of the minor scale where some pitches change, it's really important we clarify natural minor here.)
This rule works for thirds, sixths, and sevenths.
The only interval it doesn't work for is seconds. It's the odd one out; instead we just have to know that a minor second is a half step (which we define as two adjacent keys on a modern keyboard) and that a major second is a whole step.
The other intervals—unisons, fourths, fifths, and octaves—have a slightly different labeling system. If they fit in the major scale, they will also fit in the same minor scale. We end up calling this perfect, but that's a discussion for another time.