Topic „Between Composition and Improvisation“ may at first seem relevant mainly to acting and performance. I argue, however, that improvisation is equally integral to playwriting. Based on my own experience, I will show that the craft of the playwright has a bodily dimension: improvising with characters and situations —“testing words through the body”—is an essential part of writing for the stage. This can range from whispering lines to oneself, to family readings, to public staged readings. All suggest that playwriting is not purely literary but relies on an inner drive to act and perform. I will develop this general thesis with reference both to the theory of mirror neurons and to a key concept of Otakar Zich, the founding figure of Czech theatre theory, who in his Aesthetics of Dramatic Art (1931) speaks of the “inner tactile perception” experienced by both actor and spectator. I will then demonstrate how, in the process of creation, the playwright inevitably becomes both spectator and actor at once. This will be illustrated on the example of my own work on the romantic comedy Thirteen Times a Best Man, commissioned by Slovácké divadlo, one of the leading Czech regional repertory theatres. I have deliberately chosen a mainstream play to highlight that broad communicability does not preclude creativity, and that artistic research should not be confined solely to experimental works. Keywords: playwriting, improvisation, embodiment, inner tactile perception.