12 Challenges of Playing Scales in Thirds

Playing various scale patterns (instead of just playing linear scales up and down) is important because most melodies we play don’t always move up and down scale tones. The interval of the third is encountered frequently and is important to have under your lips. I have found that practicing scales in 3rds in all keys on the harmonica is actually very challenging. In the process of attempting to do this and making lots of mistakes, I have come up with the following list of 12 observations.

1. You will encounter major and minor thirds off of every chromatic tone.

When playing a major scale in thirds off of each scale degree you are playing both major and minor thirds. If you do this in all keys you will find yourself repeating a lot of the same intervals and you will, eventually, play major and minor third intervals off of every chromatic tone on the instrument. For 12 tones this creates 24 combinations. 

2. Major and minor third intervals are repeated in multiple keys

An example of a repeated interval is the minor third created by going from D to F. That interval occurs in the major keys of C, F, Bb, and Eb so gaining familiarity with that interval will help you in 4 keys. If you played scales in 3rds using minor scales that interval is used in 4 additional keys.

3. Some of these intervals are easier to play than others on the harmonica

The easy-to-play thirds include anywhere on the harmonica where the interval is produced by two adjacent holes using the same breath direction. The most obvious example is in the key of C starting from the bottom of the harmonica. C to E, D to F, E to G, and F to A.  If you keep the pattern going you have a couple of awkward-feeling intervals where the holes are next to each other but you have to switch breath direction. Those intervals are G to B and A to C. Then you have an easy one playing B to D. Those are both draw notes and right next to each other. However, there are a couple of places where you have to skip a hole to play a third and that is not an easy interval at all compared to two holes next to each other in the same breath direction.

4. The sequence of major and minor thirds generated by the major scale should be memorized.

Your ear will usually tell you if get one of the intervals wrong but I do find it helpful to know whether the interval is major or minor. I will use upper and lower case M’s to designate the series of intervals produced by playing 3rds off of each degree of the major scale. Lowercase means minor 3rd.

Here we go: M m m M M m m

So that’s 3 major thirds and 4 minor thirds produced by the major scale.

Try to get it in your head that the intervals produced from the 2nd, 3rd, 6th and 7th degrees are all minors. Of course, this order of intervals would completely change if you were playing the natural minor scale or dorian scale in 3rds.

5. Choices have to be made regarding options for F, C, and C#.

The minor 3rd interval between D and F should be played with the standard draw F and not slide F. Conversely the major 3rd interval between Db and F should involve using the blow F option with the slide. Certainly, the blow F should also be used when playing the minor 3rd interval between F and Ab. Whenever possible we should strive to keep 3rd intervals moving in the same breath direction and slide position. To be honest, the jury is still out for me whether A to C should use a blow or draw C. I have generally been trying to keep the slide out of the equation for scales in 3rds in C major. What about C#? This is always going to be a blow note but we have to decide whether to use the upper or lower option. For example, C# is available in hole 4 blow AND hole 5 blow. The major 3rd between A and C# I would aim for the lower option. However, for the minor 3rd between C# and E I would use the upper option. The rule here is to not skip holes for the interval if you don’t have to.

6. Sometimes both options for F, C, and C# are used in the same scale pattern.

Using the example in the previous point, if playing scales in 3rds in A major I would use hole 4 C# for the first interval of A to C# but switch to hole 5 for the C# to E interval. I do this same using-two-options-in-the-same-key thing for C# when playing scales in 3rds in D major. If you look at my hole suggestions for C major in this article you can see I am using blow C options but I use the lower blow C when going from A to C and the upper (hole 5) option for C to E. Remember, we are trying to not skip a hole if we don’t have to.

7. There are two places where you will have to skip a hole to produce a major third.

Bb to D requires skipping a hole. So does Eb to G. If you play scales in 3rds in Eb major you have to be aware that you need to do both of these hole skips. It’s helpful to memorize these two facts but, realistically, you need to experience the two intervals by playing them so you have muscle memory and not just mental memory.

8. There are two places where a minor third is produced on the same hole. 

G to Bb are both played on the same hole. I just mentioned the key of Eb in the previous point. This interval comes up in that key in addition to the previous idiosyncrasies of having to skip holes. C to Eb is another minor third played on the same hole but only if you are starting at the very bottom of the harmonica with C as a blow note. Otherwise, this interval of C to Eb should usually be played with the draw (slide) C option and that keeps the two notes in the same breath direction and slide position.

9. Learning scales in thirds prepares you to learn to play triads and 7th chords off of each degree of the scale.

The process of building arpeggios is all about the interval of the 3rd. However, if you play an arpeggio that is root, third, fifth, and octave then that last interval is a 4th not a 3rd. On the other hand, if you continue to stack thirds you will create a 7th-chord arpeggio and then a 9th chord. I think it’s valuable to practice 7th and 9th chord arpeggios. Any familiarity you have with playing major and minor third intervals will help tremendously as you learn to play these musical structures.

10. The third interval can be played ascending, descending and in various alternating combinations.

The first notated example shows ascending 3rd intervals when climbing up the scale degrees and then descending intervals when going back down. You could play them all as ascending 3rds or all as descending 3rds. You could alternate 1 up/ 1 down or even 2 up, followed by 2 down or the opposite 2 down and 2 up. You could play 4 up and 4 down and then reverse that. See the example below for alternating the direction of 3rds 1 up and 1 down.

11. You can and should practice other types of diatonic scales in thirds i.e. dorian, natural minor, melodic minor, etc.

This is true but I would advise working hard on the major scales at first. The minor tonalities will all eventually yield the same interval results but in a different order of major and minor 3rds. 

12. You can take baby steps

Of course, no one is obligated to join the play-in-all-keys club. Try only practicing these in 3 or 4 keys at first or by not playing the full quantity of 7 intervals i.e. just do it over the first 3 or 4 scale degrees.