Expertise refers to the set of skills and knowledge used by individuals with high abilities in various domains, including music. Studying the skills of expert musicians involves analyzing the perceptive, psychomotor, and cognitive aspects involved in musical performance. One of these skills is idiomatic improvisation, a type of musical creation performed in loco, in which the musician uses elements of musical structure and interpretation applied to a specific style or genre of music. By understanding the musical thinking of expert Brazilian pianists during improvisational solos on the same piece, the aim of this research was to investigate metacognitive strategies for teaching idiomatic improvisation in the Brazilian piano repertoire. A two-stage study was conducted. In the first stage, five improvisational solos based on "The Girl from Ipanema" (Antônio Carlos Jobim, 1963) performed by expert pianists were transcribed directly from recordings and analyzed by the researcher himself, through a comparative analysis of the structural and musical interpretation elements employed among the improvisers in each solo. In the second stage, the think-aloud protocol was administered to an expert pianist (judge) through a listening, followed by an analysis task, in which he reported aloud his thoughts during the performance of each solo. The pianist's verbalizations were subjected to content analysis. 25 musical resources and tools used by the expert improvisers were categorized. By triangulating the results of the solo analysis with the expert pianist's verbal reports, it was possible to conclude that the subjectivity of each improviser (their "way of playing") was more predominant in the improvisational solos than the mere application of objective rules regarding the sound patterns of the bossa nova style suggested in "The Girl from Ipanema." Furthermore, it was found that the pianists appeared not to be concerned with technical aspects related to fingering patterns, notes, and scales. These results have implications for the teaching of metacognitive strategies involved in learning idiomatic improvisation, based primarily on the student's constant exposure to improvisational solos created by various expert pianists, combined with the concomitant and progressive teaching of structural, semantic, and aesthetic aspects of Bossa-nova. These strategies can be expanded to teaching other Brazilian musical styles and genres, such as samba, baião, maracatu, ijexá, etc.