Transposition is a musical technique that all instrumentalists should cultivate. Every lick, chord, melody, or exercise can be played in every key, and you should try to incorporate this idea into your playing whenever possible.
The mandolin is an ideal vehicle for developing the ability to transpose. Its tuning is perfectly symmetrical: Thus, the same patterns and fingerings can be shifted easily up and down the fretboard, and across the strings. When I first began playing mandola and mandocello (both tuned in fifths, like a mandolin, but sounding down a fifth, and an octave and a fifth, respectively), I found that all my mandolin "knowledge" was being automatically transposed, like changing from tenor sax (Bb) to alto sax (Eb).
My tune "Opus 38" began life as a mandolin piece in the early '60s, and may be heard in that form on Early Dawg (Sugar Hill Records). Later, I decided that the tune sounded better played on mandola with the same fingering-but sounding down a fifth, changing the key from Am (as presented here) to Dm. Wlien I recorded the tune again in 1975 (for The David Grisman Rounder Album, Rounder Records), I played it on mandola and mandocello. If you have either of these instruments, use the tablature or read the music as if you were playing the mandolin. If you don't have a mandola or mandocello, fear not: The tune is easily transposed to Dm by shifting everything to the next lower string, using the same fingering.
Thus, the first note would be played on the second string instead of the first. (Of course, the accompanying chords would change to Dm, C, and so on, all down a fifth from those written here.)
As for the music itself, "Opus 38" is a fiddle-tune sort of piece, using open strings throughout. Notice that in the B section the open A's (or D's on mandola or mandocello) are sounded in unison with their fretted counterparts, producing a drone effect (measures 9, 11, and 13). Also note that the chords in the B section are differentwhen repeated-in measures 11 and 13, it's A minor the first time through, F major the second time-making the overall form AABB'. Have fun with the tune, no matter what key you're in!