Transformer coupled balanced in- and outputs have been and are still used with professional audio equipment to suppress common mode interferences. Using capacitors isn't a good idea generally, cause they don't provide any common mode isolation.
Nominal characteristic impedance for balanced audio is typically 600 ohm (derived from telephone line impedance). But this doesn't say much about the transformer characteristics, actually. The more important parameters are main inductance, leak inductance and possible unsatured maximum voltage capability at low frequency (e. g. 20 Hz). Also an audio signal transformer usually needs effective magnetic shielding to prevent interferences from power supply transformers.
Balanced amplifiers may be an alternative to transformers if common mode interfering voltages can be assured to keep a certain limit, as it's the case with most audio systems, e. g. stage PA.