Remarkably similar tendencies toward liberation from rigidly shaped principles occurred in art at the end of the 1950s and during the 1960s. One of those liberating forms was the instrumental theatre, and in the field of Croatian-European-World music the composer Silvio Foretić offered a specific answer. «Literary-musical-monotheatrical works», «author's theatre», «musical monodramas», «musical-action formations» are phrasings endeavouring to describe and explain what is concealed behind a part of Foretić's opus. Except for two works, which touch on the very edge of the instrumental theatre by their characteristics (Vals macabre and Quandoque bonus dormitat Orpheus), the focus is on four works - Symphonie, Semi-mono opera, Der achte Tag and F.r Klavier? - which are peculiar forms of the «Foretić-like» instrumental theatre. In this genre, the three elements that Foretić is most interested in are joined; and they are: text, action and music. Creation of their relationship prompts the composer to discover always new, original and specific solutions. It is important to stress that all these works assume a specific performing procedure into which the author integrates into as actor, singer, conductor and pianist - a versatile musician. Almost every work is created on the programmatic basis determined by the text, while sound is almost reduced to the level of «consumer goods». As the main mediator and transmitter of the author's engagement, the text is an autonomous body that takes over the function of the author's idea, notion, and action presentation. The subject is both about engagement in a sense of the composer's relationship toward the milieu - in this particular case toward the Zagreb musical-cultural (academic) circle of the 1960s and the 1970s - as well as about the conductor's/performer's (or musician's in general) relationship toward music itself, i.e. toward certain phenomena within music and the way of their interpretation. The very literary-satiric elements are those revealing the authentic orientation of the author's active engagement, while action and music form a union as additional elements (no less important).