Updated: Jul 18, 2019
When recording vocals, there are many ways to use the equipment to improve the performance. While the technical requirements to recording a vocalist can be pretty straightforward: using one microphone in a room/booth with an interface, recording software and a pair of headphones; there can be many ways to harness the equipment and technology to achieve the best performance from the vocalist.
This can make or break a vocal recording, as the use of headphones can throw off even a well trained singer. Most singers practice without headphones, therefore they are used to defining their pitch, tone and dynamics using the acoustics within the space they are singing in. Headphones essentially eliminate this and replace it with their dry voice that has been picked up by the microphone and sent back to the singer directly into their ears. This can be very unnatural and cause singers to sing off pitch, in addition to singing too loudly or softly. A simple solution to this is to remove one ear of the headphones and use that ear to naturally pitch, while the other ear listens to the music that is coming through the headphones. One downside to this setup is the potential for sound to leak out of the headphone and bleed back into the microphone, which will create a less than clean recording. This can be combatted by psychically removing one side of the headphones, so sound only comes out of one side (often seen with orchestral studio recordings), or by simply panning the music to one side of the headphones. Another approach to this issue is to keep the headphones on and use a reverb effect on the voice whilst recording; this will artificially simulate a sense of an acoustic space, giving a similar effect of helping a singer stay in pitch.
Another major issue that often occurs when recording vocals with headphones is the levels of the headphones themselves, having the headphones too loud can cause singers to sing flat and too quiet can cause them to sing sharp. It also depends on how the singer is singing along to; bass and other low end instruments are notoriously hard to pitch too whereas keyboards, pianos and guitars tend to be easier to pitch too (provided they are in tune), meaning that if possible it is best to present the singer a headphone balance that has less bass and more of these types of instruments.