In response to Duaine Hechler's query (MMD 120605), my two cents
worth.  In the world of non-mechanical music, my observation is that
anytime notes in a musical composition are changed in any way, that
is referred to as an arrangement.  That includes cases in which, for
example, the key is changed (also referred to as transposition),
notes are added or left out, or note values are changed in a way
that results in a change of rhythm.  Those are the main changes which
are most commonly made, but I suppose there are other examples.

I recently listened to a performance by a pianist who had lost his
right hand, which was referred to as, "arranged for left hand only".
The notion that an arrangement must be a case in which the instrument
upon which the piece is played is other than what the composer had
intended is, I think everyone would acknowledge, archaic.  A
transcription is most generally anything which has been translated from
one format to another, such as an audio recording or MIDI files.

I reiterate, these values for the words in question are the ones I
believe to be most commonly accepted by those involved in non-mechanical
musical performance, vocal or instrumental.  As an experienced translator,
I am qualified to report that every language has thousands of words
whose meanings vary, sometimes incredibly drastically, in accord with
the genre of speech in which they are used.  I would personally refer
to Mr. Hechler's work as an arranged transcription.

Language being an ever-changing fluid medium, I won't be surprised if
some of us survive long enough to see even these definitions change.

Lee Rothrock