In this case, need is a word that could mean different things to different people. You “could” record an album with one mic if it was a very versatile mic (like the Shure SM57 or Sennheiser MD421-II) or even certain quality condensers like the Neumann TLM102, and depending on what you are doing on that album (namely, you are not miking drums).

However, would your album sound as good as if you used microphones that are designed for different purposes? No. A good way to think of microphones is that they are like tools and work well for certain things. So ideally you want to have a few microphones that will allow you to record everything you want to record well.

The main thing that will push your need for additional microphones outside of trying to upgrade your main mic or getting a mic or 2 for a particular purpose, is recording drums.

To record drums in the most basic way that will sound good, you could use the “Glyn Johns” technique, which was developed by the famous English sound engineer of the same name, who worked with Led Zeppelin, The Beatles, The Who, The Rolling Stones, etc.

This method in a nutshell is to mic the snare and the kick drum, then use 1 overhead mic 40″ above the snare, and another 40″ from the snare just beyond the floor tom. So 4 mics are required to do this set up.

The next level up in miking drums would be to use 8 mics – 2 overheads, snare, kick, high hat, and the 3 toms.

From there you can keep going further if you have enough mics and enough inputs on your recording equipment to handle them and do things like 2 mics on the kick drum, miking the snare from above and below etc.