One of the key elements to being able to sing with a big, full, rich and resonant sound is stamina. It is one thing to make big sounds, but quite another to be able to make these sounds throughout an aria or song; and even more throughout a whole opera or concert. This most vital component is something that is not considered in vocal training today by most teachers, and especially those in universities. This is due to the fact that in those settings the teachers are required to put out singers at such a fast rate that the time needed to really develop a voice is severely curtailed. So they are forced to get singers to learn music to be able to perform in recitals which are required by the schools. This makes it impossible for big voices to thrive. Smaller voices have an easier time with this kind of curtailed process because they are less difficult to train. Bigger voices take much longer and require increased attention.
When a singer with a big voice decides to train they are dealing with developing bigger muscles. Those muscles take longer to develop. Not only do they take longer to develop, but also it takes longer for them to gain stamina. So we have two important components to training:
1) Developing the muscles needed to sing
2) Developing stamina to sustain big singing
A student will often find that in the beginning of their training that they are able to make some big, beautiful and impressive sounds. And they will often talk about how much easier these sounds are to make when they are done correctly. However, the ability to sustain these sounds throughout a musical piece is a whole other can of worms. This is where composers do not make it easy either; and in particular with bigger voices. The repertoire for more dramatic voices contain more low notes, but also many more high notes than the lighter repertoire. The dramatic singer is required to constantly go up and down the scale and also to sustain long, held out lines. This takes incredible stamina. On top of all of that the composers usually write the high note climax at the end of the aria - which only makes sense. This adds to the need for stamina.
Often I will hear young or developing bigger voices (and also smaller voices) make these big, full, rich sounds. However, since they cannot maintain that sound throughout the aria, the high note at the end will suffer. Many teachers and coaches will try to avoid this by lightening the voice so as to make it less taxing on the singer. The problem with this approach is that it skirts dealing with the issue at hand by avoiding it. When that happens the singers never reach their full potential. Instead of engaging the sound fully and gaining the stamina to do so, they are told to lessen the sound. Consequently, we never hear what the voice could have been at its prime development. This is one of the main differences in the singers of the golden age compared to the singers of the current age. The older singers had much bigger, fuller, more beautiful and richer voices. They were able to thrill us with the sheer beauty, power and mastery of their voices. This also included the ability to sing piano, decrescendo and crescendo. If a singer never gets to their full vocal potential then all we hear is the ability to hit notes instead of the ability to thrill.
Young singers and older singers alike need not forget the importance of vocal stamina. If you are making big, free sounds, but you just lack the ability to sustain them to the end of an aria do not give up on them. Remember that it takes time to build up your muscular stamina. Athletes and artist athletes such as ballet dancers know the need for stamina. And singers, being athletic artists themselves, also need to remember this fact. Stick to developing your muscles and stamina so that you can achieve your ultimate potential. There is nothing more thrilling than that.