The Underlying Physics
Although the methods and history are varied, the basics of audio recording have been largely unchanged over the years. Once the horn recording technique died out, the system was simplified.
Faraday’s Law states that an EMF can be induced by a moving magnetic field. When this is done to a conductor in a circuit, it can be used to provide power to the circuit. When this is used in audio recording, the circuit includes a device that records (usually magnetically) the electrical signals onto some medium, like the cassettes that we are used to. Thus, the signal is translated from pressure waves to electric field to magnetic recording. Recent developments skip the last stage of conversion entirely, instead translating the changing electric field directly into a digital recorder. This the process of most modern recordings, although the cassette still holds solid sway in the public.
The actual microphone receiver is
usually reliant on these principles (with a few exceptions, detailed on the
next page). These methods involve a
lightweight conducting plate placed near a magnet with wires leading from
it. Pressure from the air waves cause
the plate to move, and the moving plate in the magnetic field produce a small
electric field in return. The early
microphones needed a battery or power source to amplify it within the 
system,
but later microphones were unpowered.
This model is one of the more common. Dynamic microphones rely on a receiving cone, on the left, connected to a coiled wire around a magnet. As the air pressure pushes the cone, the coil moves around the magnet, inducing the EMF and giving a signal to be recorded. Although simple and therefore durable, dynamic microphones lack an even range of response, making them unsuitable for high-quality recordings.
The ribbon microphone is a more delicate model, but with a much better response. This is centered around a small ribbon of conductive material, which negates the receiving cone and therefore the narrowness of sound from the dynamic microphone. Unfortunately, this design renders it rather fragile, and therefore unsuitable to transport. However, its quality is superb, and it runs in competition with the condenser microphone still.
The third style is the condenser microphone, one of the oldest models still in use. It places a voltage across the two plates and uses the capacitance of them to measure the sound. As the plate shifts from the sound waves, the capacitance shifts and therefore the charge changes. This is all placed in circuit with a recording lead, so the signal is transmitted.