To find the relative minor chord of any major key you just count down three half steps. The two keys share the same notes. Using relative minor chords is a great way to transition between major and minor without changing the key signature.
If you were playing a song in D major and want to shift to a minor sound without changing the key signature, you could move to B minor.
The following example uses Minor Triads in Am.Root inversion - root is on the lowest noteE--------0--B-----1-----G--2--------D-----------A-----------E----------- A C E R 3 5First inversion - root is on highest noteE--------5--B-----5-----G--5--------D-----------A-----------E----------- C
Modes on All 6 StringsAeolianE--------------------------------2-3-5--B--------------------------1-3-5--------G--------------------0-2-4--------------D--------------0-2-4--------------------A--------0-2-3--------------------------E--0-2-3--------------------------------LocrianE--------------------------------3-5-7--B--------------------------3-5-7--------G--------------------2-4-5--------------D--------------2-4-5--------------------A--------2-3-5--------------------------E--2-3-5--------------------------------IonianE--------------------------------5-7-8--B--------------------------5-7-8--------G--------------------4-5-7--------------D--------------4-5-7--------------------A--------3-5-7--------------------------E--3-5-7--------------------------------DorianE---------------------------------7-8-10--B--------------------------7-8-10---------G--------------------5-7-9----------------D--------------5-7-9----------------------A--------5-7-9----------------------------E--5-7-8----------------------------------Phrygian E--------------------------------------8-10-12--B------------------------------8-10-12----------G-----------------------7-9-11------------------D----------------7-9-10-------------------------A---------7-9-10--------------------------------E--7-8-10---------------------------------------LydianE-------------------------------------------10-12-14--B----------------------------------10-12-13-----------G--------------------------9-11-12--------------------D------------------9-10-12----------------------------A----------9-10-12------------------------------------E--8-10-12--------------------------------------------MixolydianE-----------------------------------------------12-14-15--B--------------------------------------12-13-15-----------G-----------------------------11-13-14--------------------D--------------------10-12-14-----------------------------A-----------10-12-14--------------------------------------E--10-12-14-----------------------------------------------Modes on Bottom 3 StringsAeolianE--------------2-3-5--B--------1-3-5--------G--0-2-4--------------D---------------------A---------------------E---------------------LocrianE--------------3-5-7--B--------3-5-7--------G--2-4-5--------------D---------------------A---------------------E---------------------IonianE--------------5-7-8--B--------5-7-8--------G--4-5-7--------------D---------------------A---------------------E---------------------DorianE---------------7-8-10--B--------7-8-10---------G--5-7-9----------------D-----------------------A-----------------------E-----------------------Phrygian E-----------------8-10-12--B---------8-10-12----------G--7-9-11------------------D--------------------------A--------------------------E--------------------------LydianE-------------------10-12-14--B----------10-12-13-----------G--9-11-12--------------------D-----------------------------A-----------------------------E-----------------------------MixolydianE--------------------12-14-15--B-----------12-13-15-----------G--11-13-14--------------------D------------------------------A------------------------------E------------------------------Modes on Top 3 StringsAeolianE-------------------B-------------------G-------------------D--------------0----A--------0-2-3------E--0-2-3------------ w h w w h wLocrianE-----------------B-----------------G-----------------D--------------2--A--------2-3-5----E--2-3-5---------- h w w h w wIonianE-------------------B-------------------G-------------------D--------------4----A--------3-5-7------E--3-5-7------------ w w h