- Records include correspondence, lists of dues-paying members, and receipts. The names of Carl Metz, R. Emmett Vaughan, and Charles F. Hencken, president, secretary, and treasurer of Local No. 502, figure prominently in the records. "Musicians' Protective Association" appears as part of the name of the local in many records.
The bulk of the material relates to the payment of dues to the union, and some records concern the rental of the German Artillery Hall for the organization's meeting and for concerts by the Metz Band.