Welcome to... "Micro-Lesson 259"
The Open "E Major," tuning is a slightly less popular open style tuning compared to those like; "Open G," and "Open D." The issue, (to some degree), with Open "E" tuning is the tightening of strings to establish the tuning itself. Generally, we do not tighten guitar strings since they inevitably want to quickly de-tune back down-ward causing a host of issues with the open chord we establish. Therefore, using an older set of strings, or by keeping another guitar off to the side permanently tuned to a tuning like this will yield better results for stability.
Open E tuning is a tuning for guitar where we establish the strings as; low-high; E-B-E-G♯-B-E. This produces an, "Open E Major," chord. In the example piece that I've composed for this Micro-Lesson, the tuning is applied to a "I-IV-V" chord progression from this key.
In measure one, we begin with a lick that highlights the tonality of "E Major." This phrase helps pull us upward into the V-chord of the key (B major). The open 5th string "B" pushes us through a harmony that connects us into the 3rd measure where an open "A" chord is highlighted from the 5th fret of 6th string and uses the open 4th and 5th strings to support this harmony.
The fourth and final measure takes full advantage of the IV and V chords, (A and B major), to produce a turnaround that can work to either loop the riff, or to resolve it back to the tonic chord of, "E Major."
Be sure to use a tuner when you are going to change your tuning to open "E", and check it repeatedly for the first hour while you study this riff. Remember, that we're tuning the string up-ward, and the guitar does not like this up-ward "stretched" direction. Enjoy!
Micro Lesson 259: "Open E Major Tuning" Folk Riff