Hi Simon,

"Nevertheless, I still have a difficulty:
are you implying that we cannot determine the mode of a melody without
adding harmony? If so, that's an important principle that I was unaware
of."

In my music theory classes, I was always taught to look at the entire
structure of a piece rather than the melody line.  I don't know whether
this is applicable to folk/pop music but I would suspect that it is. 
One of the first things we did was to determine the harmonic structure
and key of a piece.  Even the most sophisticated of classical music
(except contemporary 20th century) at least started on an established
key with predominant I IV and V (or i iv V if minor) in most cases. 
When getting into the Impressionistic era (Debussy, Ravel, Faure) the
modal systems came back into vogue so if you saw an unusual harmonic
sequence or tons of accidentals that was a clue that you might consider
a mode OR a whole-tone scale OR a pentatonic scale  In other words, the
harmony got you on the highway, and the melody found the address.

"My consideration of the Beatles' tunes was done by taking them away
from
their musical settings and dealing with them in isolation, on the basis
that
there are many quite different ways of arranging a tune. I quite accept
that
the musical settings that the Beatles provided may not have been in the
least modal. But doesn't the same thing happen with folk songs when sung
by
pop groups or arranged (say) for orchestra?"

It shouldn't matter unless the underlying harmonic structure is totally
re-done, in which case the piece would be too altered to recognize.  Of
course there are court cases where composers have been sued because of
the stealing of a melody line and putting a different harmony under it. 
One of the most interesting (and frustrating) aspects of music analysis
is that there are no absolute rules to follow - ie, if the arranger or
composer WANTS to put in some strange borrowed chord, he/she can without
the music police coming after them :-)

  If you do treat the Beatles
tunes I mention extracted from their harmonic settings I don't see why
you
can't consider them as modal. "Yesterday", for example, has no
accidentals
in the melody line. - which brings me back to my original question.

I don't have the music for Yesterday, but when I played the melody on
the piano making sure I ended in E I used F# and G# in the ascending
"all my troubles"  E F# G# A - then when the melody descended, the F#
and G# were natural.  This tells me immediately that when finishing on
E, you are playing in the key of a melodic minor.  The scale goes like
this:  ascending:  a b c d e f# g# a  then descending: a g f e d c b a
Does this agree with your melody?

Carol


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