Problem with Tags

[Patrick Karl]

I'm having a problem trying to learn how to use tags.  The following snippet:

\version "2.14.2"
music = \relative c' {
        \tag #' low   {c}
        \tag #' high {c'}
        d e f g a b c
}

\score {\new Staff { \keepWithTag #'low \music }
            \layout { }
}

\score {\new Staff { \keepWithTag #'high \music }
            \layout { }
}

should produce IMHO two c major scales, the first one starting at middle c, and 
the 2nd one starting at one octave above middle c.  However, there is a problem 
with the first scale, namely, the first note is middle c, but the rest of the 
scale is shifted up an octave.  It almost looks like the c' in the expression 
tagged "high" has had an effect on the score containing \keepWithTag #'low.

If I switch the two lines, containing \tag, then both scales are identical, 
both starting one octave above middle c.  Again, it looks like the c' tagged 
"high" has an effect on the score containing \keepWithTag #'low.

Should that happen?