The following from the DCMS own consultation document would seem to make it clear that only a musical instrument provided without any means of amplification is excluded by the proposals.

1.3 The proposal would also ensure that the provision of musical instruments (such as a piano made available to members of the public to entertain themselves) is excluded from the definition of regulated entertainment. For clarity, this exemption will extend to items provided to enable a musical instrument to be played without amplification. This is intended to clarify that ancillary items such as music stands are also excluded from the definition of entertainment facilities.