The piece is written in a range of styles, from jazz and blues to classical and folk music. Say's use of improvisation and aleatoric elements adds a sense of spontaneity and freshness to the work, making each performance unique.
If you want to play this piece legitimately and support a living composer, purchase the official PDF from Schott Music . It's an investment in high-quality engraving, correct fingerings (if any are provided), and legal peace of mind. The price is reasonable for a professional-level concert piece.
Fazil Say's works, including Summertime Variations (based on Gershwin's "Summertime"), are likely protected by copyright. As a contemporary composer (Fazil Say is alive and active), his compositions are legally protected, and distributing or downloading unauthorized copies of sheet music violates intellectual property laws.