The Upper Trapezius is a fairly large muscle, so it may require a bit more heat to aid in its healing. I would recommend applying the warm sandy beaches of Aruba or Bali in Februrary to this muscle. If that is not possible, a second recommendation is to enjoy a hot-tub after having sipped a six ounce dose of fermented grape juice pain killer. If that solution is still not an option, I would finally recommend a hot bath, and you can splurge and add a cup of Epsom Salt and dream about Aruba and Bali for a steamy hour.
To Stretch your Upper Trapezius
1. Place the back of one hand on your lower back making sure you are keeping that sides shoulder down
2. Place the other hand gently across the top of your head, while the head is looking straight forward
3. Apply gentle pressure to your head pulling your head towards the hand on head side until you feel a good stretch, no pain. (Do not push down)
4. Hold the stretch for 20-30 seconds and perform for both sides 3 times
This muscle connects your shoulder-blades to your neck and spine, and is used to help hold your left arm (and violin) steady. Your right Upper Trapezius also gets a workout, but your right (bow) arm has freedom of movement - it is allowed to move. In particular your left-hand Upper Trapezious is held still and is often under tension. Keeping this muscle immoble and tense for long periods of time makes it very angry, and it expresses it anger with pain.
Steps to alleviate shoulder pain:
1. Massage the muscle to release tension
2. Apply Heat
3. Periodically Stretch
4. Pay attention to your shoulder muscles and consciously relax your shoulders when playing
The Upper Trapezius is a bit hard to reach by yourself, so it might be easier to have a masseuse or chiropractor work this muscle.
Baring that, there are some ways to massage the pressure points of this muscle yourself.
There are a number of back-massage products on the market such as the "Thera Cane", which allows you to easily massage knots on your back and shoulder:
Holding your arm upright for and hour or two at a time, while at the same time keeping your shoulder imobilized, puts a great deal of strain on your shoulder muscles. Of particular interest to us today is your left-hand Upper Trapezius:
Now we get into the Zen of playing the fiddle. There are so many things to keep track of while playing: notes, bowing, bow location, bow pressure, left hand fingering, right hand wrist and elbow action, pitch, tone, and don't for get to breath... and all this while we also need to relax!
The main requirement here is an awareness of our own bodies. What does it feel like to be tense? What does it feel like when we have two muscles fighting each other to keep our left shoulder stationary? I would recommend reading the works of Kató Havas in dealing with stress and performance.
Some of her workshops are available on youtube: