EVP (Electronic Voice Phenomenon), is a means of recording spiritual voices on tape. It is widely believed to be communication between our dimension and the spiritual dimension. There are a lot of groups who actively research EVP under strictly controlled conditions, they capture EVPs during paranormal investigations, and others research EVPs as their main area of work. There is a wealth of information available on the Internet about EVPs. This includes information, examples and how to start recording EVPs on simple basic equipment.

Some things to be aware of

Most people use dictaphones or cheap analogue recorders. Whilst the recorders will pick up sounds they are not shielded from man-made out side interference such as mobile phones, radio etc.

The way all tape recorders work is very simple. A microphone and recording head i.e. an audio amplifier connected to a coil of wire (recording head). This is also the basis of a normal radio without an RF tuned front end. However, connect a piece of wire to the amplifier microphone input, and under the right conditions, it will pick up transmissions. These may be what most people record.
Another thing to be aware of is low frequency sound, sound that is lower than we humans can hear (infra sound) or sound that is so low in volume that you will not be aware of it. However, put a recorder on the table and the table will amplify the sound like a sounding board on a musical instrument. You will get a muffled incoherent sound recorded.

We are not saying that all EVPs are not real, it's just you need it be analytical and skeptical in your approach to these experiments.
Digital does have it flaws too but the way it stores your information is better. With tape you will always get tape hiss. This on its own will make you hear all sorts of things in the background. The human brain will make patterns out of any input it receives i.e. sound, light, touch, etc. and sound is a very deceiving source of information. Direction, amplitude, pitch all have their oddities. Echoes can be a great source of misleading information as the echo will not be from the source direction and also could be reversed several times distorting the original sound.

Digital recorders also only record a very, very small amount of acoustic information (4 and 8 bit sampling is common). Since the human ear and brain does not need all frequencies to be able to decode sounds that are fed in to our ears, the brain tries makes sense of any input. Whether it be complete or incomplete information, the brain will piece it together and most often, it's correct in its deduction and interpretation. However, it can be fooled by this 'pattern matching'.

Analogue recorders record approx. 70% of sounds that could be picked up, but the tape hiss is white noise (all sound frequencies together) so again you will hear things in the 'hiss' that make sound patterns then, once again, your brain will do the rest.

Okay, possibly the best way of recording EVP is to use a high quality recorder and high quality tapes, also if possible use a second recorder of a different make. This will help eliminate bad screening of the circuitry on one of the recorders. What you are looking for is an EVP on both recorders. Ask questions and see if you get a response. This will also eliminate radio transmissions or someone next door talking