A number of recent technological advances in mobile devices have affected the various and vibrant researches on mobile music technology. In especially, the research about new reper- toire-based ensemble using mobile phone as the primary musical instrument like MoPho(Mobile Phone Orchestra) of Stanford University is representative in mobile music making technology. In these studies, new performance paradigm is suggested. Taking advantage of the phone`s mobility, ubiquity and accessibility, the once distinctive roles of a composer, performer, and audience have been blurred. However, breaking down spatial limitation, a performer has a tendency to depend on own improvisation rather than a score and has difficulty to communicate with other performer for exchanging their performing status. This research presents a system that can support a performer by providing communication infrastructure between performers in a mobile phone ensemble. The system has two facilities; 1) monitoring performer`s status in performance 2) providing an instruction message to control a mobile instrument. To archive this purpose, available interactions on a mobile phone will be categorized and an instruction level is analyzed by user test. It will be suggested which instruction level is proper in a mobile phone performance through the analyzed result for conclusion.