Font shapes for different sizes

[Noeck]

Dear Abraham,

I have a question to you, but I thought perhaps lilypond-users are also
interested:

When I use smaller glyphs in a score (change clefs, cue clefs, a solo
voice above the piano part, etc.), LilyPond usually uses a different
font such that the font weight harmonizes with the other standard-sized
objects. When I choose one of your fonts, my impression is that this is
not really the case, but the glyphs are just scaled. Perhaps you can see
what I mean in this example:

\version "2.19.21"
%\paper { #(define fonts (set-global-fonts #:music "cadence")) }
{ a \clef treble a \cueClef treble a }

If the \paper line is commented out (using Emmentaler), the smaller
clefs look bolder than with Cadence.

Is that true? Is that intended or is it just a drawback of not using
metafont for the font creation?

Cheers,
Joram