  The algebra of so-called shifted symmetric functions on partitions has the
property that for all elements a certain generating series, called the
$q$-bracket, is a quasimodular form. More generally, if a graded algebra $A$ of
functions on partitions has the property that the $q$-bracket of every element
is a quasimodular form of the same weight, we call $A$ a quasimodular algebra.
We introduce a new quasimodular algebra consisting of symmetric polynomials in
the part sizes and multiplicities.
