Is Hauptwerk needed for the Notre Dame de Budapest sample set?
No, this sample set doesn’t require Hauptwerk. NDB Pipe Organ Samples is designed to operate with compatible data streaming samplers such as GigaStudio* or Native Instruments Kontakt.
For the .GIG (GigaStudio 3) files, GigaStudio 3 or later or compatible is required.
For the .NKI (Kontakt 2) files , Kontakt 2 or later or compatible is required.
*Note that GigaStudio is a sampler software that is discontinued and not available for purchase any more, but several other sampler software can import, interpret and load GIG files.