The major pentatonic scale produces simple, attractive and easy-to-harmonise melodies by avoiding the two semi-tone steps in the major scale - the fourth and seventh.
This limited, five-step scale is an ideal opportunity to develop your play-by-ear (aural) skills - not only because there are only five rather than seven scale-tones to choose between, but - as I hope you'll agree - because the major pentatonic scale is 'nearly music already', and so, easier to 'get'.
The first thing you want to know about a tune you're trying to play by ear is whether it goes up, down, or stays the same.
We're going to make it easy to concentrate on that by using (and creating) melodies which start on the tonic and are symmetrical as far as up and down is concerned.
Here's an introduction to the basics.
Let's start building some melodies using major pentatonic scale-tones one and two steps either side of the tonic (starting/home note).
Here's the table for that tune. Play it from the table a few times.
Here's a second combination that fills up our eight-bar template.
Here's one we just make up 'on the fly'.
Nothing spells out the way music's put together as well as transposing it into other keys.
Here's a preparatory video for exploring the tunes in D.
Here are the three tunes in D, all in one video. The tables are in order beneath.
You should be able to play the tunes in D from the tables alone.
Now an all-in-one video taking our tunes into B flat - another one-black-key major pentatonic scale.
Play the tunes in B flat from the tables.
Now see if you can 'doodle' (compose!) your own eight-bar tune using the one up/down and two up/down building blocks.
Also, practice humming the three tunes from the tables to check you know your pentatonic major scale tones T - 1 - 2 and T - 6 - 5.