In the 80's he turns more towards orchestral music and finds inspiration in the works of great composers of the 20th century such as Stravinsky, Prokofiev, Shostakovich, Alberto Ginastera and Aaron Copland, but also in the avant-garde and electronic music of Karlheinz Stockhausen, Pierre Schaeffer, Edgard Varèse, La Monte Young, Terry Riley and John Chowning, Krzysztof Penderecki, György Ligeti and John Cage and composing works on the basis of such inspiration, while on the other hand being inspired by alternative rock and progressive music (Keith Emerson) and the works of New York music and art scene, with artists like John Cale, Andy Warhol and Brian Eno, and authors like Tom Waits and Nick Cave.
Hajsek composed, arranged and played for many famous Croatian and Bosnian rock bands and their members (Bijelo Dugme, Divlje Jagode, Drugi način,[8] Vještice, Peti Element).
In that period came two interesting cantatas for choir and orchestra "Mother", "Next to the river of Babylon" and "Wave" for eight voice choir, "Antistema ghithago" electrophonic music, 2nd Symphony, and the music for great animated series "The Pomkiners" which has undergone numerous broadcast around the world (Canada, United States, UK, Australia, Sweden, Norway, Switzerland etc.)
Musical works of particular interest from this period, amongst others, were "Sonata for piano and percussion", "Allegro Spicatto" for chamber orchestra, "Fuga Primavera" and "Fuga Polaris" for big orchestra, "Symphony of Istria", "Opera Furiosa", string quintet "In the evening" and "Mare Stellarum" electrophonic composition.
[13][14] The main difference in terms of traditional film and theater music and composer's concept is that the composer's works in the field of theater and film are complete musical forms, so in fact representing concert works intended for independent concert performance.
The project, based on book by Igor Weidlich, was, at the time of its opening, the first original Croatian musical in more than a decade to be performed at the Zagreb Theatre Komedija.