I suppose it's actually a joke at alto singers' expense. I'm not familiar with the stereotype, but does it imply that they have a limited range? (EDIT: See correction by MRC, below)

    pseudonym58 changed the title to (humor) A Piano of Extraordinarily Narrow Range .

    The cliché is not that the alto singers have a narrow range, it's that the parts they have to sing are extremely boring. See for instance:

    The very narrow piano is a sculpture by Bjorn Perborg. It doesn't play.

    17 days later

    pseudonym58 Nailed it!

    Case in point

    Altos are bottom right, and not that this piece in itself is boring.