By the connection cable is the first way to solve this problem. This is a very direct method. There are suitable jacks in stereo that is used for any type of portable music. This mp4 player can be plugged in this jack through a connection cable. Generally these connection cables are of standard sizes so that they can be fixed to all types of cars. The auxiliary jacks can be used for other types of devices also.
Apart from the above the up methods, the music player can be played on the stereo by connecting it with the receiver of the stereo. This is very useful when there is a need to play mp4 player. The mp4 player can simply be connected to the receiver through a cable that is given for connecting purposes. This is available with the mp4 player. If there is a stereo receiver that is replaced by the previous one that was obtained with the stock car, there may be provisions for other devices known as auxiliary connection.
Played even through a cassette player is also a good way. In the stereo, the adapter can be plugged in the jack that is used for the headphones. This is very easy and gives good quality music as above. This needs an adapter. If the stereo consists of tape deck, the adapter can be connected between the player and the stereo.