Knowledge about musicians’ attentional focus may shed more light on why some succeed in demonstrating their optimal performance under pressure while others fail to do so. In previous research, attentional focus has not been investigated directly after performance. The aim of this study was to extend and deepen our understanding of the “what” and “how” of musicians’ attentional focus during performance under pressure. Qualitative data provided by 46 violinists and violists in open-format questionnaires immediately after they performed audition excerpts under low- and high-pressure conditions were analyzed using thematic analysis within a constructivist framework. Findings revealed that the focus of upper string players during “real-life” performance may be more dynamic and multifaceted than previous research might suggest. In particular, when participants reported a music-related focus, they referred to the level of formal and technical elements and to the level of interpretation and character, but also to prioritizing between the two levels. They focused on the navigation of these music-related aspects, their physical and emotional performance experience, critical thoughts and attempts at control, and the quality and dynamic of their focus. Furthermore, they described ways of managing their focus in a positive and adaptive sense but also reported negative thoughts, feelings, and sensations. Staying in the present moment and enjoying the music was thus a desirable focus. Approaches based on mindfulness and acceptance may be particularly suited to supporting musicians in maintaining a beneficial attentional focus during performance.