A keyboard unit includes: a key; a plurality of members which include the key, and each of which has an engaged section for forming an engaged state, the engaged state changed by turning of the key, at least a portion of the engaged section formed of a conductor; a detector which is configured to detect information on the engaged state of the plurality of members by detecting a conduction state between the at least portions of the engaged sections which are in contact with each other; and a determiner which is configured to determine a musical sound parameter based on a detection result of the detector.