Sarievski's grandson, also called Aleksandar, told media the last piece heard in the film is in fact Macedonia's folk classic "Go Down, Go Down Clear Sun", penned by his grandfather.
"We'll wait to see the results of the investigation by the (Macedonian) Association For Author Rights," he was quoted as saying in Friday's Dnevnik daily.
"If we don't reach agreement, we'll explore other measures."
The Zack Snyder-directed portrayal of the 480 B.C. battle between the Persian army and a band of Spartans has already incurred the wrath of Iran.
Tehran denounced the movie as a Western bid to vilify Iranians, depicting their ancestors as ruthless but repeatedly outsmarted by the Greeks. The film has yet to open in Macedonian cinemas but pirate copies are widely available.