compound interval

17 LETTERS · STARTS WITH C

compound interval is a valid 17-letter word worth 26 points in Scrabble and 34 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

C3O1M3P3O1U1N1D2I1N1T1E1R1V4A1L1

3 + 1 + 3 + 3 + 1 + 1 + 1 + 2 + 0 + 1 + 1 + 1 + 1 + 1 + 4 + 1 + 1 =26 PTS

DOUBLE WORD → 52TRIPLE WORD → 78

MEANING

What does compound interval mean?