Hints for Spelling Major and Minor Thirds

  
     Look at a piano keyboard. If you remain on the white keys (no accidentals) you will notice that some thirds have 2 black notes between the upper and lower white keys, while some have only one. Those with 2 (F-A, G-B, and C-E) are the major thirds. All others have only one black key between them and are minor thirds.
     Staying on all white keys C-E, F-A, and G-B are all major thirds, the others are all minor thirds.
     Sharps move a note up, flats move it down. Always think in terms of moving towards or away from the other note. Moving the upper note up makes a larger interval, while moving the lower note up makes a smaller interval. Moving both notes in the same direction doesn't change the interval.
   If you know your key signatures, any time the upper note is in the major key of the lower note it is a major third. (i.e. C-E: There are no sharps or flats in the key of C major, so E is in the key of C major, so C-E is a major third.)