Google information on modes of the Major scale, or search the threads here - there have been a few exhaustive discussions about them, IIRC. Anyway, in a nutshell, each note of the Major scale is the starting (root) note for a mode that is composed of the same notes in that parent Major scale, but aligned differently. The different alignment gives them minor or Major tonalities, which you just discovered with the F# minor (this is the 6th mode, Aeolian).
The names, intervals, and tonalities of the modes are (using C major for ease):
1. C Ionian - Major - C-D-E-F-G-A-B (think Allman Bros/Dickey Betts)
2. D Dorian - minor - D-E-F-G-A-B-C (think Carlos Santana)
3. E Phyrgian - minor - E-F-G-A-B-C-D (Spanish jam sounding)
4. F Lydian - Major - F-G-A-B-C-D-E (shows up in jazz a lot)
5. G Mixolydian - Major w/b7 - G-A-B-C-D-E-F (think...what's that guy's name??? oh yeah Jerry Garcia!)
6. A Aeolian - minor - A-B-C-D-E-F-G (natural minor scale)
7. B Superlocrian - B-C-D-E-F-G-A (don't really know of anyone that uses this one much)
Anyway, you should notice how these modes all use the same notes, but because of the intervals between them (either Major or minor 3rds) are Major or minor in nature. If you want to really get inside the type of jamming that the Dead or the Allmans did, then you must get a handle on modal playing. "Kind of Blue" by Miles Davis is kind of the Bible for modal playing, you should give it a few listens while working on this stuff.
This is also tied in with how the Major scale is harmonized, btw. For instance, in C major the chords of the harmonized scale are:
So each mode "fits" over the chord it goes with in the harmonized scale.
Out of the loop? I didn't know there was a loop!