Watch the Stretched Thin online guitar lesson by Brad Carlton from Chord Studies: Open String Chords Vol. 2
This progression is a vi-IV-V in the key of E major. The first chord which is a C♯madd9 is a bit challenging because of the stretch but just remember to relax your hand and position your thumb on the back of the neck. Then we move to the Asus♯4 which gives us the sound of the Lydian mode due to the ♯4. Notice on the Badd4 we don't want to use a barre because we need to have that first string ringing open.