In Italian, the word falsetto comes from the word “false,” which implies that it is not a true, technically sound form of singing. This is not 100% accurate. However, the falsetto sound in the upper range of the male voice strays greatly from a unified modification of vocal registers (which I’ve discussed in previous posts), and creates a very different sound from the rest of the male voice.
Falsetto is often used to “lighten” a sound in the male voice, and is a common technique that we work on in singing lessons. Some male singers, when having trouble using a full-voiced, resonant tone in the upper range, rely on falsetto simply to get a high note to sound, when they fear they might be pushing the sound out through excess tension. It can be seen almost as a safety net for those who are not secure enough in their technique to sing a high note in a full head voice.
The result of using falsetto is a lighter tone, with less resonance and less control. The singer is not as easily able to adjust volume, pitch or access to overtones when using falsetto, as opposed to full head voice. It can often be breathy or raspy sounding, and contains no connection at all to the chest resonance that can still be used up to a certain point in the vocal range.
While falsetto may be very useful in choral settings, when a powerful, full-voiced tenor might interfere with the blending of a full ensemble sound, I do not generally recommend it for solo singing. While building up the vocal technique to handle a full head voice takes some time and muscle building, I believe it gives a singer more control over their voice and a more pleasant, consistent sound overall.