Michael - actually I was asking something a bit different, which is how come so many accompaniments seem to use *more* than the three 'obvious' chords. For a fairly extreme example, take Nick Drake's song "Time has Told Me". Simplified a bit, in the verse there's a C-F-G chord progression, but the first time through he gets from the C to the F via Bb ("A troubled cure"), and the second time through ("For someday our ocean") via Eb. Then the chorus alternates an Eb with an E7. Eb to E - three flats to four sharps - madness, I tell you!

I've never seen the sheet music for "THTM", what with copyright and everything, but the C-F-G suggests to me that the melody's in C. But then there's a Bb chord (Bb-D-F), an Eb (Eb-G-Bb) and an E7 (E-G#-B-D) (hmmm, see what he's done there...) - if you were writing that out in dots there'd be accidentals all over the show.

Piers - that looked fascinating but I didn't get very much of it; you seem to have started with Lesson Four!

He seemed to be saying that a C-E-G triad becomes different chords depending on the key signature.

No, 'he' was saying that if you take a piece of music paper (or a copy of BarFly) and write the notes C, E and G on a single staff, what you have written becomes different chords depending on the key signature. Perhaps it's not the most obvious way of looking at it, but I thought I'd made it reasonably clear what I was doing.

A bit more background, in reply to Don and Anahata - my cunning plan is to accompany myself on "The Wind and the Rain", based on the version sung by Johnny Collins. The chords only come in on the refrain; transposed to suit my voice, they go

Note:   A                        G
Chord: F                        C
         Oh, the wind and the rain
...
Note:   G               F                   E
Chord: C               Dmi                C
         Crying in the dreadful wind and rain

Not a lot to it - and it's fairly easy to hear which notes 'want' a chord behind them. I certainly never considered chording every note!