For this article, I would like to consider only a single human voice. That makes things simple, or does it?
Let's start with how many microphones you need to record a single human voice...
For classical music you might want to use more microphones to capture the ambience of the recording space, but for any other kind of recording then you just need one microphone for a single human voice.
It's worth saying here that for any single instrument you might use two mics to make a stereo recording. But a single human voice has no useful stereo content, so one mic is fine, and it will capture a stable image where two mics may not (there is further info from Audio Masterclass on this here...).
So you need to own just one mic, yes?
Well yes. If you have a microphone of basic professional quality, you can record a single human voice to a professional standard. Of course you'll need good sound insulation and acoustic treatment in your studio, but a microphone as good as the Shure SM57 or better has the ability to deliver professional results.
I would go further and say that there isn't any other microphone, no matter how expensive, that will make your work more professional. Just different.
And that's the key - 'different'.
Different microphones have different sound characteristics. So you might want to have a microphone that captures a very natural sound (like the DPA 4011), or a microphone with a classic neutral sound (Neumann U87), or a microphone that flatters the singer (AKG C12 - You wish!), or a microphone that has the classic rock sound (back to the Shure SM57).
Also, different microphones suit different singers. A mic that sounds good on one singer might not sound so good on another, where a different mic might be better. This can vary from day to day so it's always worth setting up two mics and seeing which is best before going for a take.
So the quick conclusion to this is that all you need for professional results is one mic of at least basic professional quality.
But if you want to optimise the sound of your vocal recording, then having a selection of mics available is better.
One more thing...
I said at the start of this article that I was going to consider a single human voice.
Well this covers speech as well as singing, and there is an important difference.
The priority in singing is that the recording sounds good. The priority in speech is that the recording (or broadcast) is easily intelligible. You might consider a mic that is known for its suitability for speech such as the Electro-Voice RE20 or Coles (STC) 4038.
All of these matters are covered in the Audio Masterclass Music Production and Sound Engineering Course, with audio examples. In particular the components Microphone Comparison Speech Tests (Module 2, Component 2.4.1) and Microphone Comparison Singing Tests (Module 2 , Component 2.4.2).Come on the FREE COURSE TOUR