When audio recording was in its infancy, recordings were made live in a room with all acoustic instruments. Because the human voice can be easily overpowered by the strength and clarity of electrified guitars, booming drums, and loud keyboards, one of the most commonly used and effective techniques when recording lead vocals is the process of double-tracking. In all but a few niche examples, the more power and sonic weight a part carries, the better results in the mix and mastering stages.
One of the most sought after qualities for an audio recording to possess is strength and fullness of tone. WHAT YOU NEED TO KNOW ABOUT DOUBLE TRACKING VOCALS What is Double-Tracking?