Sonodyn is an investigational device that within this clinical investigation is intended for use in patients suffering from low back pain, tension headache or neck pain, originating from therapy-resistant myofascial pain syndrome. Myofascial pain syndrome is a prevalent pain condition in the adult population and a common cause of pain and dysfunction in the musculoskeletal system. It is a trigger point-induced regional musculoskeletal pain disorder affecting one or more muscles or groups of muscles. Sonodyn is a handheld medical device that combines low-energy ultrasound, electrical and magnetic field stimulation for non-invasive transcutaneous treatment of chronic myofascial pain syndrome. Sonodyn is a battery-operated, rechargeable stimulation device to be placed over specific trigger points for associated pain patterns in the human body. It emits ultrasound, electrical and magnetic stimulation signals with a pre-defined set of parameters for each of the independently operated power sources. The study will follow a prospective, randomized, sham-controlled, double-blind parallel group design. It will be conducted as a multi-center investigation at 6 sites in Austria and Switzerland. Patients are randomized in a 2:1 ratio into Treatment and Control. * Active Sonodyn therapy (Treatment) * No therapy (Sham Control) Two types of Sonodyn devices will be used: a fully functional one for Therapy arm patients that can deliver stimulation, and a non-functional one for Control arm patients that cannot convey any energy signals to the device output. The devices will look fully identical. Randomization will be stratified by study site, pain diagnosis and sex of the patient. For each subject, after a screening phase of 1 week, patients will be treated for 3 weeks with a follow-up of additional 8 weeks, adding up to 12 weeks. During treatment patients will activate their device 3 times a day for 10 minutes each. During screening, treatment and follow-up period, all patients will twice per day report the average and maximum intensity of their pain Numeric Rating Scale (NRS). Patients will also enter the date, amount, and time of intake of rescue medication, if applicable. The primary objective of this study is to assess the impact on pain. Secondary objectives are to compare the performance between active therapy and sham, as well as to correlate changes in pain intensity with other pain related scales.