If you can hardly sing at all, is it good to try to sing a little bit of everything all at once or just do one thing?
We really don’t know the answer to this question since the idea of cross training (in an athletic sense) hasn’t really existed before, in terms of singing. We don’t much know what goes on with kids who grow up singing in several styles, and continue singing them well and for a long time into adulthood, most particularly if one of those styles is classical.
My guess is that a lot depends on the individual, the type and amount of training, and the goals of the student and teacher. We don’t have any literature in the field to guide us, nor research. Too bad.
Writing strictly from my own personal experience, I would say that it is probably true that most young singers benefit from what has been the generally available approach in classical training. That’s pretty simple, actually:
Stand up straight, breathe in “down low”, tighten your belly as you exhale while singing and aim the sound “towards your face”. Relax your jaw, open your mouth and keep the sound steady, looking for your preferred version of “resonance”. Learn rep, in the monster yellow book first, then add the Germans and the French. Maybe, also, add the Brits and a few Americans. Go sing.
A well developed head register usually has to be cultivated deliberately and takes some time to really work. Most people are chest register dominant, so finding head register and making it work is usually a good idea, as it will help balance the sound overall and prevent chest register from causing problems.
If you are going to sing other styles, however, you also have to make sure your lower or chest register functions well. If you go by one of more typical approachs to teaching CCM styles, you simply stick closely to speech, get louder as you go higher, put in the consonants, aim the sound “into the nose”, and don’t worry about sounding “ugly”. Learn songs.
If you want to sing anything else, just do whatever you do, learn to “support” and hope for the best.
If you have any trouble with any of the above, especially in working them back and forth alternately, good luck. You either figure it out or you get into trouble. It’s up to you how to put the divergent styles together and make them partners rather than enemies.
Not a way to cross train, I would say.
If you want to learn about singing you have to learn about making vocal sound across the board and about the interface between speech and song. Sometimes they are related and sometimes they are not. What David Daniels does has very little to do with normal male speech. Likewise Diana Damrau. No normal adult female speaks in the pitches above C6 or high C but a coloratura soprano sings there quite frequently. Most high belters are singing in a pitch range and at a volume level that is far away from speech, too. And, if you speak at a conversational level and in a typical pitch range you are far away from what a trained actor would do with her speech in a play. There is much to learn and much to cultivate. What kind of interaction is most beneficial in learning more than one approach at the same time?
Again, from a purely objective point of view, we don’t know.
What I think would be ideal is for the student to sing in just one style for at least two years without having to deal with anything else. Then, slowly, other functional parameters could be introduced. Typically, however, there isn’t that luxury of time so we see a lot of students learning technique (not necessarily function) and classical repertoire from classical teachers who also have to teach them music theater songs (but who are not necessarily also teaching a different kind of function) at the same time. Sometimes the students also sing, gospel, rock and pop as well.
There are also many occasions a student who is a great belter has to learn to sing “classically” in order to get into a college music program or voice department. It can take time to do that, too, but it’s certainly possible. Is there a “best way” to do this? And, if the kid wants to be a big fat belter but the parents require that the young woman get a college degree “in music”, is it a plus to disrupt naturally good belting just to learn “An Die Musik”?
In the long run, the more the teacher understands what he or she is doing, and what the goals of the training process are, the better the odds are that the student will succeed. The more the student is motivated and has decent ability at the outset, the better the odds are, also, that the student will succeed and that, in a few years (2 to 3), the capacity to sing decently in a classical sound and a commercial music sound with equal success will emerge. The ability to specialize, though, might not be possible unless the singer has some clear goal of a career in a specific field and knows what the expectations of that field are in terms of the vocal quality and style.
The potential for the vocalist to end up like scrambled eggs also exists in this approach. The student can easily be confused and the voice can end up exactly nowhere. That often leads to discouragement and to giving up, particularly if the teacher blames the student for this “failure” as is typically the case.
If you find yourself in a position of having to train young singers in more than one style, most especially including classical styles, you need to really know what you are doing. If you guess or just dabble you run the risk of really disturbing the equilibrium of the student’s voice and psyche. Remember, first, do no harm.