The words below share an interesting quality. Can you determine what it is?

ARE
FATE
VOTE
TRAIL
LIONS
VIOLA 
CAROL
TANGO
ORGAN
MACHO
CALLER
UMPIRE

HINT:
It has to do with vowels.

Answer:

The two vowels in each word can be interchanged to create a new word, with no other re-arrangement of the remaining letters. These words are a specialized set of anagrams.

ARE - ERA
FATE - FETA
VOTE - VETO
TRAIL - TRIAL
LIONS - LOINS
VIOLA - VOILA
CAROL - CORAL
TANGO - TONGA
ORGAN - ARGON
MACHO - MOCHA
CALLER - CELLAR 
UMPIRE - IMPURE

Credit: Mike Nelson
VOWEL SWAP