In the overtones of any note, lets take C as example, appear some useful intervals. For note C they are represented by E, G, D and B. (D appears later than E and G, because it is less consonant.) We can create some chords with these notes, these are:
C = C-E-G
CM7 = C-E-G-B
Csus2 = C-D-G
Cadd2 = C-D-E-G
What gives? When we reverse the chords (equivalent to consider undertones instead of overtones) and then shifting the new root back to C, we get
C reversed = Cm, C-E♭-G.
CM7 reversed = stays a CM7. An M7 (or maj7) chord is quite common.
Csus2 reversed = Csus4, C-F-G. A sus4 chord appears quite often.
Cadd2 reversed = Cmadd4, C-E♭-F-G.
Now, is "minor add 4" an actual chord in the sense that is used?