This C#m11 has the root (C#) at the bottom, so it isn’t a slash chord. However, if we look at the two lowest notes, C# and E, we have the root and b3rd, which set this up as some kind of C# minor.

One guitar is playing a I IV V progression using E7, A7 and B7 chords while the other is playing two different parts over the progression. The first part is an E7 triad without the E note, mixed with ...