The purpose of this study was to investigate the perception of professional music teacher identity (PMTI) among stringed instrument teachers who are alumni of the University of South Carolina String Project (USCSP) preservice teacher education program. Using a fixed mixed method design, I first surveyed all USCSP alumni from the past 20 years using the PMTI Questionnaire. For the qualitative portion of the study, the researcher interviewed three USCSP alumnae in their post-second stage of teaching (year 11-20). All USCSP alumni identified, rated, and ranked their expertise in subject matter, didactical, and pedagogical aspects. USCSP post-second stage alumnae also identified and ranked their expertise using current and past video stimulus from their preservice teaching in 1997. The results of this study indicated that experience, knowledge of oneself, adaptability within one's contextual environment, and reflection are the main components within PMTI development across career stages. All USCSP alumni were a combination of all three aspects- subject matter, didactical, and pedagogical expertise. Their possible changes in PMTI across career stages, however, require a receptiveness to professional development and adaptability to one's teaching environment. Results from this study also indicated that authentic context learning environments, such as the USCSP, and video stimulus as a reflection tool help mitigate attrition across inservice teaching career stages. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]