By permuting the melodic tuning for 4-courses instruments, 3m-3M-3m which is an open tuning we get the 5-6m-5 which is again open tuning but with intervals of 5.
IN THIS WAY IT RESEMBLES THE MANDOLIN TUNING EXCEPT IT IS AN OPEN TUNING
E.g.
A2-E3-C4-G4 OPEN TUNING FOR Am7
or
E2-B3-G4-D4 OPEN TUNING FOR Em7
