For naming intervals I have two strategies in my head.
- First identify the generic interval between the two given notes by counting the notes between them (inclusive of those two given notes themselves)
- Look at the root note. Imagine the major scale for that particular note. If the given second note belongs to the major scale, then the interval is major and I also write the identified interval number detected in step 1. But if the note does not belong in the imagined major scale then it depends on the number of the interval. e.g. if it's fifth, then it can be only diminished, augmented, or perfect.
An example would be C Gb
- Generic interval is 5th.
- Therefore the interval quality can be either dim, aug, or perf.
- C major scale is C D E F G A B C
- Gb does not belong there, G belongs. Gb is half a step lower, therefore, it's diminished
- The interval is dim 5th.
Using the charts provided by www.musictheory.net. i.e. counting the number of half-steps included between the two given notes and see where they fit in the charts below.
Now I have got two questions:
- Are both strategies equally good? Are they prone to errors? Can any of them fail for a particular interval?
- Are there other faster/better strategies?