Hey! Can someone recomend me somegood lessons sites that explain chord substitutions! I figured out that substitutions have just about all to do with knowing what notes are in a chord and chords that have similar notes can be substitutes. Correct me if im wrong. Im getting into this whole theory seriously but i need some help!
Here is how I see substitution:

back up - view harmony from a wider viewpoint. In a ii-V, the ii harmony can be played in so many different ways, depending on how you're situated. Or even take a single chord and play something completely different that still does what that chord does.


This is really hard for me to put into words but take for example the most simple subs - triad subs: On a dm7 chord play a dm triad and then an em triad. They both create the ii harmony over a D bass note. The tritone sub: really the way I see this is just you're playing an alt chord, a perfectly acceptable way to play V. Or instead of playing a V chord, play the ii-V. Go the mile with Coltrane changeup and substitute a cycle of ii-Vs that return over a boring old ii-V.

Basically you can see harmonies in 2 ways: resolved and unresolved. As long as you can hear it, you can have any unresolved harmony you want. Just remember that the weaker the resolution, the more you need to hear it and mean it to make it sound right.