Dealing with muscular tension in singing
What is tension?
Not all tension is bad! In fact the reason you're able to sit upright in front of computer right now and read this is due to muscular tension. This is helpful tension. However, some types of tension interfere or are not productive for the task you're trying to perform. This is unhelpful tension. Unhelpful tension in singing may be defined as anything that interfers with free and efficient vocal function.
Singing involves an integration of many processes - posture, respiration, phonation, resonance, articulation and expression. Unhelpful tension in one part of the body (or process) can easily interfere with others. For example, a tight jaw will affect you ability to communicate text (articulation) AND your ability to produce beautiful vowels (resonance). Similarly, tension in the abdominals will alomost always lead to squeezing or tightness in the throat.