Perfect is a synonym of Pure. Pure is similar to Theoretical. Theoretical is the opposite of Practical. 
Mutter is a type of Sound. Wave is part of Sound. Wave is related to Hang. 
Perfect <--Synonym--> Pure <--SimilarTo--> Theoretical <--Antonym--> Practical 
Mutter --IsA--> Sound <--PartOf-- Wave <--RelatedTo--> Hang 