Watch the Sub IV Major for II Minor online guitar lesson by Robbie Calvo from The Modal Alchemist
I'm playing a B minor 9 chord in the backing track for this example and superimposing a D major 7 arpeggio over that to create my melodies.
The major 7th of the D chord is also the 9th found in the B minor chord so we'll be able to target that tone specifically for a very sweet sound. You'll also hear me bend a minor 3rd interval from the note B up to D very Pink Floyd darling!
I'm sure this concept of chord subs is sinking in well with you now and you can hear the value it can add to your melodic improvisations.