 | unisons become octaves and octaves become unisons |
 | 2nds become 7ths and 7ths become 2nds |
 | 3rds become 6ths and 6ths become 3rds |
 | 4ths become 5ths and 5ths become 4ths |
 | major intervals become minor and minor intervals become major |
 | perfect intervals remain perfect. |