First a little background. I use enhance in the title because I constantly see, in both live performances and in the studio where people turn up the bass Eq to try to add bottom, beef or warmth to an instrument that is mostly mid-range. You cannot add what is not there and this practice generally add nothing but mud to the sound or mix. In addition, there are many variables when capturing a performance in both live and in the studio that can affect the sound. Warmth is also a confusing term and is described in many ways. In addition, there are many theories surrounding what results in the lack of warmth in a mix. This covers several topics and is beyond the scope of this subject.
The first thing we must assume is that the equipment used is of good quality and capable of producing frequencies throughout the audible frequency range. Without full frequency representation a balanced well-rounded sound can never truly be achieved.
Reverb is just sound bouncing around a room. Reverb can be artificially created as with spring reverb and other types of artificial reverb units. It can also be created utilizing IR or impulse response. Impulse response is reverb that is created in a space by making a tone or sharp blast or even a starter pistol. This is recorded and the impulse removed leaving just the reverb tail. Reverb is constantly used in post-production studios to give content the exact sound of a particular space, examples would be people talking in a car or an alley a large or small room, you get the idea. It can also give a real feel to recorded music. It is widely used in a music recording industry to create space. Now to the meat. Even though a A440 note has a primary frequency of 440 Hz additional frequencies evolve and run up both the high and the low end of the audible frequency range. When handled properly these additional resulting frequencies give the note a full well rounded and natural sound. As mentioned earlier reverb is just sound bouncing around the room and it’s well known that some rooms sound good and some sound bad. Finding a room or space that enhances and allows the frequencies to breath and develop gives you that clear warm, beefy sound everyone is looking for. The key here is proper reverb use can enhance all frequencies more evenly producing a natural enhanced sound. This goes a long way in creating music that is clear well rounded with the warmth good recordings are required to have. Several techniques are used to provide a larger than life mix or live performance but reverb is a powerful tool widely underrated and misused. Engineers who understand the power of reverb will create a more powerful mix. Live sound engineers who understand the effects of space will also provide a much more powerful mix.