Amateur recording method. Listening to the recording with headphones, sing the song from beginning to end, including the recorder or the function in the phone. In principle you can use any recording device, from which you download the recording to your computer.
Install a sound editor on computer, open the music file without voices. Download on computer recording voice, open in the same editor, on the neighboring "minus one" track. Drag so that the words and the music matched the rhythm.
This method of recording the voices low quality, lots of noise and overtones, a low clarity of consonants. In addition, often the music and the voice of "crawl" in the tonal and rhythmic plans. Part of the defects can be removed by the forces of the supports, but truly beautiful voice will not work.
Professional method. Open minus the soundtrack in a audio editor. Adjacent the track to activate recording. Connect a microphone to the sound card, enable recording. Sing the song in chunks, stopping peresushivaya and overwriting the wrong place.
In some cases, often to save time and money voice record at a time, without stopping and rewriting. The quality suffers greatly.