Dear Reinhard,
If it starts and ends on F, it is in the key of F. The main three ways I know to do this are:
- No capo. Hit the chords (F, Bb, C are the 1, 4, 5) and roll for backup. For lead, find the melody (the root note, F, is found on strings 1 and 4), and try to make it work with rolls. That's the hard part.
- Capo 3 and play as though in D. The 1, 4, 5 chords are D, G, and A. For playing in D with no capo, the fifth string is usually raised 2 frets' worth, to A. For F, you'd raise it 3 frets (like the regular capo) past that, so it's a C. Hopefully you have spikes or a 5th string capo for that. Don't tighten the string 5 frets' worth!
- Capo 5 and play as though in C, with C, F, and G the main chords. Fifth string is raised 5 frets.
All three of these might be good options. I like #1 and #2 best, as they allow the low F note into the sound, which gives it more warmth.
Good luck!
Pete Wernick