Thirds can be major, minor, augmented and diminished. Below you can see that the number of half steps determines the quality of a third:
Major third, 2 whole steps or 4 half steps:
Minor third, 1 1/2 whole steps or 3 half steps:
Augmented third, 2 1/2 whole steps or 5 half steps:
Diminished third, 2 half steps:
A third can be identified by analyzing the seconds between the lower and higher notes and a middle note inside the third. For example, the third C-E has two seconds: C-D and D-E. Using the following table we can find out the quality of the third:
|If the seconds are:||then the third is:|
|minor - minor||diminished|
|major - minor||minor|
|major - major||major|
|augmented - major||augmented|
Following this method we find that the third C-E is a major third because both seconds (C-D, D-E) are major seconds.
If any note has accidentals, we can determine the quality of the interval without accidentals and then analyze the effect of the accidentals:
See I > Intervals for related entries. To learn about go to Tutorials > Intervals.