Instrumentation amplifiers are, in a sense, the upgrade to an operational amplifier. They are often fully differential, and come in a few different configurations.

The two op-amp configuration is limited to a minimum gain of 2. However, it has two major advantage:

The three op-amp configuration excels with

Fully differential amplifiers are amplifiers with differential outputs. Link instrumentation amplifiers, there are several t

This TI chip gets a special mention, as it is the first fully-differential instrumentation amplifier IC. It is an expensive part at GBW, PSRR, THD+N @ , slew, stability with up to loads, high CMRR, unity-gain and attenuating stable.

Main disadvantage: low common-mode voltage.

Programmable gain amplifiers are generally aimed towards low-frequency (DC/near-DC) amplification. For the audio space, a PGA made with a digital potentiometer and an instrumentation amplifier may be appropriate, though ICs should be able to be made with better precision or functions to improve precision. Generally speaking, for audio, gain precision is less important than stability. One wants a logarithmic taper

Variable gain amplifiers are often aimed towards high speed signals. Potential interesting audio uses include dynamic modulation such as compression, envelope control or AM.