4

Alternative method using scales

Within a major diatonic scale, there are four perfect and four major intervals above the tonic of that scale.  In the following example, these intervals are named from C (tonic) in the scale of C major.

Using this method, you consider the bottom note of the interval a major tonic and then determine the major or perfect interval above that (2, 3, 6, 7 are major; 1, 4, 5, 8 are perfect) based on the key signature of that major tonic.  Finally, as in previous exercises, you determine how the accidentals affect the quality of the interval (e.g., decreasing its size by 1/2 step).  Obviously, with this method, you need to know your major key signatures really well (not a bad idea!).

In each of the following examples, try to complete the exercise before checking the answer.

1. Write:  Step 1:  Step 2: Step 3:

2. Write:  Step 1:  Step 2: Step 3:

3. Identify:  Step 1:  Step 2: Step 3:

4. Identify:  Step 1:  Step 2: Step 3:

When all else fails, try this:

The quality of an interval can also be determined by counting the number of half steps within it. This is very tedious in the long run, but it will get the job done. Keep in mind that your first task is to determine the number size of the interval, then the quality can be established by counting the number of half steps in the interval. Following is a chart showing the intervals and the number of half steps in each:

Interval Number of half steps   m2 (or A1)   1   M2 (or d3)   2   m3 (or A2)   3   M3 (or d4)   4   P4 (or A3)   5   A4 (or d5)   6   P5 (or d6)   7   m6 (or A5)   8   M6 (or d7)   9   m7 (or A6)   10   M7 (or d8)   11   P8 (or A7)   12

Take a look at #1 above. You are asked to write a m6 above Eb. According to the chart above, a minor 6th has 8 half steps. Now look at a piano keyboard. 8 half steps above Eb is B (natural). E to B, though, is a 5th (E-F-G-A-B), not a 6th. 8 half steps above Eb and a 6th is Cb--the enharmonic equivalent of B.

Now look at #4 above. You are asked to determine the number size and quality of the interval from Gb to D (natural). G to D is a 5th (G A B C D). There are 8 half steps from Gb to D. According to the chart above, a P5 has 7 half steps. A perfect 5th (7 half steps) made larger by one 1/2 step (8 half steps) is an augmented 5th.