Audio file used by Kontakt, a professional audio sampling application; saves a "monolith," which combines the audio samples and the patch information into a single file; enables the data to be stored together instead of in separate files, which can cause file path referencing problems.

NKX files save the audio information in a proprietary format. Therefore, sometimes audio engineers prefer to keep the sound samples separate from the patch information so that they can use the samples freely with other applications. NOTE: More recent versions of Kontakt use .NKS files for monolith container files.