A good classical singer has to have at least two octaves of usable range. A CCM singer, not so much, although it could be helpful. A classical vocalist is expected to be very familiar with at least four languages and preferably speak them: Italian, French, German and English. Other languages are also valued. CCM singers generally sing in English unless they have a reason to choose another language for artistic reasons.
Classical music runs from the 14th century (early manuscripts) to the present day. That’s a long time. Early Music specialists have dug up obscure scores in dusty libraries and old churches and are always arguing as to what is the most correct performance practice, based on writings of the same time periods. Each style of classical music has it’s own scholars and experts and not all classical singers, even professional ones of high stature, know everything about it all. People specialize in various eras, composers, languages and styles. There is sometimes vigorous disagreement about vocal and musical approaches amongst those who are recognized scholars, and things do change, slowly, in what is expected, both vocally and musically.
You do not need to know one single bit of this information if you sing CCM styles. You might also specialize in a certain CCM style, and then you would be expected to know that style. Most of our CCM styles are from the late 19th and early 20th century, but spirituals go back to the mid-1800s and folk music goes back to the earliest settlers. Music theater has been heavily influenced by the English, primarily, but also in more recent years the French as well and now by the Latino culture. Jazz, America’s gift to the world, has many different aspects and there, too, there are specialists in various threads. New Orleans, big bands, blues, bebop, swing, fusion and many more, each have their own characteristics. Rock music, also very American in origin, has spread all over the world and in the musical lingua franca of our times. You could specialize in jazz or rock history and not know too much about country music or folk music, and vice versa. Country music is centered in Nashville and it is a large, highly successful arena in which there are many very famous singers and most of them have no need to know anything about other styles or even about formal vocal technique.
CCM singers use all kinds of sounds a classical singer would never use including vocal sounds that are noisy, scratchy, breathy, nasal, pinched, distorted, and deliberately slightly above or below a pitch for a moment as an expressive tool. They use or don’t use vibrato, deliberately or accidently, as a part of style. Many CCM styles require movement, which classical singers generally don’t do except as they might move in an operatic roles. Classical concert and orchestral singing, recitals and oratorios are presented with the vocalists standing in one place.
So, what, if anything IS the same?
There are a number of things which are the same. Everyone has a larynx, two vocal folds, a throat, tongue, jaw, mouth and lips, a pair of lungs, a torso and a brain. The sounds are made by those same body parts for everyone in the same way. The vocal folds close and vibrate on a pitch or over a succession of pitches (in a glide), on a vowel or a closed sound like a hum, while the vocalist is exhaling. There is much research to suggest that the mechanism functions optimally (but not that it can’t function if things are less than perfect) when the posture is erect, aligned and strong (but not stiff) and that the inhalation is easy, deep, and freely taken. The exhalation is moderated between the open rib cage and the abdominal muscles (primarily the rectus abdominus). Extending both the duration and the pressure of the exhalation while sound is made is a learned skill for both speech and song. We understand language best when the muscles that effect articulation work easily and accurately. That’s it. “Resonance” or the acoustic efficiency or the spectral envelope of the sound may vary widely and no one pattern is always used with the exception of classical singers who generate the “singer’s formant cluster”.
If you still think classical singing is a “one size fits all” vocal training you live in a bubble of your own creation.