Guitar skills: Stretch fingers and tonal textures with these progressive rock chords...
Three of the chords use open strings to add size and space to the chords. This is a trick often used by players like Alex Lifeson of Rush and John Petrucci of Dream Theater.
The F#add9#11 chord has a bright Lydian mode flavour and instantly brings Steve Vai or Joe Satriani to mind.
The Mikael Åkerfeldt-style F#m add9 is somber, but also very colourful - perfect for an Opeth song.