| 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. |