Joerg, if you read the linked study in my last message you will see that there are styles of singing that cause greater muscle tension in the larynx. I'm sure you don't want to cause nodules on your vocal cords, so as you try to create this break sound when you sing, warm up first and keep your muscles as relaxed as possible (learning how to do this well is where a good classical voice teacher comes in). The more you tense them up, the more harm you can do. When you learn good breath support, too, the making of sound is more effortless. Alot of people push the air or belt through their vocal cords to get volume. This causes much more tension than supporting and controlling the air flow. Here's a bit of description just from the discussion part of the study.
"The normal biomechanical configuration for effortless phonation is that the vocal cords approximate "like two hands clapping on a hinge"; vocal cord closure is achieved along the length of the vocal cords, without the participation of supraglottic structures. (There is neither front-to-back foreshortening nor side-to-side compression of the larynx, and the aryepiglottic folds remain thin and rounded.) "Effortless phonation," however, is not always what singers exhibit when they are singing. "
"...It must be emphasized that the data we present here do not suggest that singing styles associated with high Muscle Tension scores should be avoided, nor do they suggest that a high MT score is in any way abnormal or pathologic. They do, however, make one assumption (which is supported by clinical experience): High MT scores imply high levels of laryngeal work, whereas low MT scores imply relative vocal/laryngeal efficiency. "
"Generally, some variables appear to decrease the Muscle Tension score, or "protect against excessive laryngeal tension," and these include: (1) vocal training; (2) singing classical styles of music; and (3) warming-up before singing. Intuitively, each of these variables should exert a score-lowering influence. "
My input on this subject is that learning classical technique helps you use your voice for singing in ANY STYLE you choose to, and provides technique that enhances your voice as well as your vocal health (preventing vocal nodules) and keeping your voice longer into old age. Don't feel that by knowing these techniques that you can't sing anything but classical music! That's simply not true! Any singer of any style of music can benefit from knowing good vocal technique.