When an acoustic guitarist plays a note, there are variations in the way the note can be played that affect the sound; the manner and intensity with which the string is picked or plucked, the pressure on the fret, the cleanliness of the string, the angle of the sound hole to the mic, and other factors play a part. The human voice is an even more complicated instrument.
1) Take time to listen to a singer’s unique voice
Depending on the application, such as singing solo or with a choir, trained singers can deliberately enhance the acoustic energy in sections of their vocal range. Before recording, take time to listen to the singer’s unique voice and how it sounds on that day, in that particular room. Be flexible and tailor the session to capture their natural personality. Use a frequency analyzer to make room in the mix to fit the frequency response of the singer.
2) Make the performer feel comfortable
Do everything you can to make the performer feel comfortable. Take time to consider the room temperature, lighting, ambiance, and other features of the recording environment. Adjust the singer’s closed-back headphone mix for level, compression, and reverb. If the singer is off pitch by under- or over-singing, adjust the level of their voice in the headphone mix to bring it back in tune. The headphone mix has a recursive effect on the recording. If the vocalist feels comfortable and confident, they will perform better, and the recording will benefit.
3) Experiment with different microphones
Select whatever microphone you have that best flatters the singer’s voice. Experiment with different options. For a lot of music, you will often use a stand-mounted large diaphragm cardioid pattern condenser with a shockmount and pop shield. Sometimes a more modest handheld dynamic microphone like a Shure SM58 works better with a vocalist’s tone or live performance style. Adjust to the needs of the situation.
4) Coach the singer on how to work with the microphone
Gently coach the singer on how to work with the microphone. Explain proximity effect, which is how the bass sounds get louder as they get closer to the microphone. Show the singer how to manage the distance to the microphone to control dynamics and prevent disruptive plosives (popping sounds) and sibilance (harsh "ess" sounds). However, don’t get carried away with too much coaching. Provide light, encouraging feedback between takes, and never interrupt the singer mid-passage. Remember that the comfort and confidence of the performer is paramount.
5) Record multiple takes
Record the passage multiple ways with some variation. It can take time for a vocalist to warm up and find the right vibe. Even if you think the singer nails a performance on a particular take, record the track again. Multiple takes will give you more material to work with when you mix.