Marion - I found the following definition of pastoral here. http://members.tripod.com/~dorakmt/music/glossary.htmlPastoral: Pieces in imitation of the music of shepherds. The characteristics are fast triple (3/8) or compound (6/8, 12/8) metre, Siciliana rhythm, moderate time (often siciliano and larghetto), tender, flowing, lilting melodies mainly in conjunct motion, notes flowing along in groups of threes, prominent use of parallel thirds, repetition, long-held drone bass on dominant or tonic. Oboes and F major are the most pastoral instrument and key, respectively.
And then Beethoven's 6th Symphony (did I mention that it's my favorite?) is discussed here. http://members.tripod.com/~dorakmt/music/beeth.html
The musical features of the Symphony No.6 that give it a pastoral character can be listed as follows: the key of F major and the extensive use of woodwind, especially oboe which has originated from the shawm (a shepherd's instrument); the use of fast triple (3/4), compound duple (6/8) and compound quadruple (12/8) time in the third, last and second movements, respectively (but not Siciliana rhythm); widespread use of pedal basses, simple diatonic harmonies (mainly tonic-dominant) avoiding minor key modulations and chromatic chords; upper parts moving in thirds; bird-song imitations; second movement in subdominant; significant repetition; playing down the dramatic features of sonata form in the first two movements (like the lack of dominant preparation before recapitulation in the first movement) and lack of sudden dynamic changes.
Bach's "Sheep May Safely Graze" in an instrumental. I couldn't find the original score, so I'm not sure if it's in the key of F. I heard it one year at a funeral at Christmastime in a medley with "O Come All Ye Faithful."
I think Handel's "He Shall Feed His Flock" starts out in the key of F. (couldn't find my music to that tonight) If not, the pastoral interlude that preceeds it is probably in the key of F.
All this to say, I'm always surprised at how composers use various keys for various moods. Conductors also. Leonard Bernstein was not above tuning the orchestra slightly sharp to get a fresh, bright sound.
Mary