I have only one ear that works (bad genes perhaps). The solution from my audiologist is the Phonak system. One small hearing aid for the good ear, and a mini transmitter that sits on the dead ear, thus giving me the equivalent of two-ear hearing. The system is provided with a small separate control on which I can select the range of response- wide (for music, etc.) and voice range for general hearing. Expensive, but worth it.

Some time ago I saw a link to a company providing a hearing aid for musicians with one good ear; both channels from a sound system are fed into the good ear. Cost a few hundred, so reasonable.