The composers behind the iconic Halo soundtrack are suing Microsoft over unpaid royalties. 

As reported by Eurogamer, Marty O'Donnell and Mike Salvatori allege that Microsoft owes them royalty payments dating back 20 years.

The pair helped create what's arguably one of the most recognizable scores in gaming, including the legendary "monk" chat that has become synonymous with the Halo franchise.

Lawyers representing O'Donnell and Salvatori initially filed the lawsuit in Washington in June 2020, bringing six causes of action against Microsoft including a breach of contact, unjust enrichment, and tortious interference.

Speaking to Eurogamer, O'Donnell claimed he and Salvatori have been trying to settle the matter with Microsoft for the last decade, but finally decided to take legal action after failing to make any real headway.

There are a lot of moving parts, but O'Donnell and Salvatori's are essentially arguing that they created and licensed the Halo music to franchise creator Bungie while trading as O'Donnell Salvatori Inc., claiming that Microsoft owes them royalties as a result.

In a counterclaim, Microsoft said the soundtrack was created under a work-for-hire agreement and as such it qualifies as the author of the work. O'Donnell refutes that assessment.

"It was never work-for-hire," said O'Donnell. "It was always a licence deal. So that's what we did with Halo. With the first Halo music ever, that was written and recorded in 1999 for the first time. It was licensed to Bungie. Bungie didn't get bought by Microsoft for over a year.

"At the time, the Halo music, for this very nascent beginning thing called Halo, was still owned by O'Donnell Salvatori and licensed to Bungie."

Check out the full report from Eurogamer for a more comprehensive breakdown, including additional comments from O'Donnell and Salvatori.