There are lots of really good op-amps suitable for or specifically designed for low noise audio use but the most popular configuration is the dual package (for many good reasons).
Having established that my client for the refurbished 'boutique' mic pre-amp doesn't mind if it's non-original provided there's an improvement, does anyone have any favourite candidates to replace the venerable NE5534 ? Bipolar or fet input, I don't mind, the noise source impedance at the op-amp non-inverting input is ~ 1200 ohms.
Graham