Music teacher here:

Treble and Bass Clef are just two floors of the same building. The floor of one is also the ceiling of the other. (middle c)

Every instrument has a floor where they are more comfortable, but some spend so much time going up and down the stairs that it makes sense to build
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A room somewhere in between. (Alto and Tenor clefs) to save them some effort once they get used to it.

We could redesign the whole building so that every floor is identical to solve some of the prolems and create sone new ones. There are also accommodations that will make the it more accessible.
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