A player piano or hybrid instrument retains classification here as long as its essential character is that of a stringed keyboard instrument — meaning it has a string-and-hammer action that produces acoustic sound, even if augmented by electronic player mechanisms or digital sound systems. A purely electronic keyboard with no strings would classify under electronic musical instruments. The presence of a functioning acoustic string action is the decisive factor.

For high-value instruments, CBP expects a commercial invoice detailing the make, model, serial number, and agreed purchase price, along with any manufacturer's price lists or dealer invoices that corroborate the declared value. For used or vintage instruments, an independent appraisal from a recognized piano technician or auction house record is advisable. Serial number records can also help establish the instrument's age and provenance, which affects both valuation and, for antique instruments over 100 years old, potential reclassification.