Each musical instrument has both a vibrating mechanism and a resonating mechanism. The vibrating mechanism is the source of the sound waves, and the resonating mechanism refines, augments and amplifies those sound waves giving the instrument its unique tonal character. A few things that make the voice vastly different from every other instrument include the fact that the vocal folds can simultaneously be stretched, thickened or thinned, changing the nature of the actual source of the sound waves; in addition, the vocal tract of the human voice can change shape on a dime which enables a singer to sing a huge amount of different vowel sounds, give their voice a seemingly unlimited number of colors, and also adding the dimension of language to the instrument. The fact that the human voice is vastly more complex than any man made instrument gives singers a lot of options, but this complexity also makes it an instrument that is extremely difficult to “play.”
Consider for a moment the strings on a guitar. The gauges of the strings used for the lowest notes are much thicker than the strings which are used to play the higher notes. The gauges of each string are strung gradually thinner for each of the six strings in turn as the open pitches ascend. If the player wants to raise the pitch of one of these strings, they press down on the string at the fret board, which causes the string to get tighter and more stretched making the string vibrate at faster rates. In addition, they can choose different strings in order to obtain different pitches and timbers based on the variety gauges and different tensions of the tuning of each string.
A singer uses a similar principle as a guitarist; but rather than fretting, the singer stretches the vocal folds longer and tighter to raise the pitch, and shortens the vocal folds to lower the pitch. A singer can also change the thickness of the vocal folds while they are singing, thus changing in effect the “gauge” of the folds at will. One problem that singers run into is that the mechanisms which control these two operations, tend to be antagonistic to one another and can be extremely challenging to coordinate.
Singers also face the fact that in addition to having a plethora of options available in regards to the vocal folds, they also have a lot of options as to how they shape their vowels, and thus how the vocalized sound is colored. The vocal tract (primarily the pharynx and mouth) can be thought of in a similar way to the bell on the oboe, or the soundboard on the guitar. Can you imagine if a guitarist’s instrument kept changing shape with each passing thought they had? It would be a tremendously difficult instrument to play. Yet that is in effect what singers deal with each time they sing. In addition to having to find a balance between the different vibrating mechanisms and the resonating mechanism, there is also the added challenge of having to do this while using a balanced breath flow, which gets the entire body involved in the process.
As if it wasn’t tricky enough balancing the air, vocal folds and resonators of the voice, singers also have to deal with the phenomenon of muscle recruitment. Unwanted muscles get involved in the singing process, such as the swallowing muscles, the tongue muscles, the jaw muscles and the muscles around the solar plexus. These recruited muscles tend to hamper good sound, and can often tire the voice.
In a nutshell singing is a balancing act. Singing is one of the noblest of all arts. The technical side of things is an ongoing process that will keep unfolding for you for the rest of your life. Be patient, stick with it and enjoy the journey. The human voice is a gloriously complex musical instrument and all the work that goes into building it and training it pays huge dividends.