The quality of a compound interval is the quality of the simple interval on which it is based. Some other qualifiers like neutral, subminor, and supermajor are used for non-diatonic intervals.
the quALITY of a coMpoUnD iNtERvaL Is The quaLIty of THE Simple InterVAl on wHicH it iS bASeD. sOme OtHer qualifIers liKE neUTraL, suBmInor, anD supERmajoR are. uSEd For Non-diatONic IntervaLs