Composite or plastic molded articles used in a grand piano piano action. The articles make up a piano action with less dynamic mass which is, thus, more responsive to the piano player. In addition, the new action provides the extremely valuable collateral benefits of increased efficiency of manufacture and maintenance. Low inertia grand piano piano action comprises a repetition base with one or more of the following: an angled main beam, an angled balancier support beam, an integrated jack button stop, and a means to optionally connect a rest cushion assembly. Low inertia grand piano piano action may also comprise a heel with extremely low mass.