Improvisation is a defining characteristic of traditional Iranian music. Iranian musicians describe their music as ‘impossible to play in the same way twice’ or ‘able to be performed in many ways,’ emphasizing that they do not perform prepared compositions. What exactly do musicians play and how do they play it? How does the musician's individuality and originality come into play? What norms are acquired during the learning process that make improvisation possible? What is the concept of "improvisation" in Iranian culture? The author, a researcher as well as a santur player, explores these various points based on field studies and personal experiences from studying and playing traditional Iranian music over many years. This auto-ethnography is an attempt to academically elucidate the senses, physicality, and mentality of musicians by engaging with the subject through first-hand participation.