This study investigated the effectiveness of flow teaching as directed to the practice and performance of instrumental music in the post-secondary context. Its purpose was to determine the effectiveness of a three-lesson educational flow intervention for twelve post-secondary brass and string instrumentalists. Data were collected through measures of subjective experience during practice and performance and the objective assessment of three performances. Flow experiences have been studied extensively in sport since the 1970s, and consequently, training strategies have been developed to increase flow levels in sporting contexts to maximise the possibility of optimal experience. However, in the domain of instrumental music, flow training strategies have not been thoroughly developed, researched, or applied for practice or performance purposes. Therefore, it is not known what potential effects, if any, applied flow theory strategies might have on instrumental practice and performance experiences or performance outcomes. The study employed a mixed method approach using recognised qualitative and quantitative methods suitable for an educational intervention research investigation. The methodology was a quasi-experimental intervention with non-equivalent control using concurrent triangulation comparative mixed method design. This provided the simplest form of baseline design with two groups and allowed each group to act as both an intervention group and a control group maximising the possible data collection for the small sample and short timeframe. The participants in the study were 12 self-selected undergraduate string and brass players from the Bachelor of Music course at the Queensland Conservatorium Griffith University (QCGU), Australia. They were stratified and randomly assigned into two groups of six. During the Intervention phases of the 38-day study, each participant received three one-to-one Flow Music Method (FMM) lessons created by the researcher. The FMM was based on the work of psychologist Mihalyi Csikszentmihalyi and other flow researchers. Across the timeline of the study, participants completed an experience sampling form (ESF) to measure the details of their subjective experience during each practice session and immediately after performances. In addition, a video journal was recorded at the end of each practice session and a post-study interview completed. At the end of the study, an expert panel of two music assessors rated the level of performances of each participant in randomised order using a Performance Assessment Form compiled by the researcher for that purpose. All data were analysed using SPSS and NVivo to ascertain the effects of the FMM Intervention on the participant experience of practice and performance and to examine the rater assessment of performances. An investigation of the relationships between practice and performance experience and rater assessment was subsequently undertaken to determine any relevant findings. Results showed that the experience of participants during instrumental practice became more positive for both groups in terms of Mood, Flow, Last 5 minutes of practice, and Overall experience from Phase 1 to Phase 2 across the timeline of the study with effect sizes ranging from small to very large. Findings also revealed that the experience of participants during instrumental performance became more positive with higher levels of Mood, Flow, Last 5 minutes of performance, and Overall experience found in both groups for the performance immediately after the Intervention when compared with the baseline performance. The greatest increases were found for Group 1 for the scales of Flow and Last 5 where there were statistically significant and very large effects. These findings provided support for the positive effect of the FMM Intervention on the practice and performance experience of both groups.The analysis of the objective ratings of performances by two expert raters showed sufficient correlation of the global scores, however, no conclusions could be made concerning the relationship of the global scores with the practice and performance experience of participants. It is recommended that further studies of a similar nature be conducted to facilitate a deeper understanding of the relationship between the subjective response of the participants and the objective assessment of their performance. In addition, it is proposed that the FMM be adapted to ameliorate any identified challenges and to enable the most effective application to instrumental pedagogic contexts in future.