We can learn a lot from really simple songs like Three Blind Mice. Don’t laugh!
This song oscillates between I and V in the key of G in this example. I’ve provided some basic sheet music in two voices where the bass line uses root movement (G to D back to G) for each melodic phrase. Each phrase starts and ends with a chord tone (G B or D). So B A G twice, D C B twice, then G F# E F# G D. So the same chord progression is used for 3 different melodies.
Here is the Three Blind Mice TAB. We can expand the basic root movement (G D G) by using other chord tones for smoother voice leading. We can also embellish the melody. But this is a good framework to build upon.
Here is a video of some variations of Three Blind Mice written by John Thompson. It starts out in key of G, modulates to key of Bm (the dominant of G is D major or B minor) which is very common modulation as it is a ‘close’ key with one extra sharp) then in Variation II goes to Gm. It’s well worth analyzing Variations on Three Blind Mice.
-Simple melodies and simple chord progressions (eg I V) can be effective
-Modulate to closely related keys (one more/less sharp or flat). eg C to G or C to F
-Melodies with chord tones on strong beats will usually sound good
-Start with a basic framework then embellish with more notes
Please check out my Baroque Improvisation Course if you’re interested learning more of this.