Not convinced it is pipe organ. Here is some info on Tubipora musica identification. From Arkive.
"Unlike most corals, it is not colourful polyps that make organ pipe corals attractive, but instead, their dark red coloured skeleton (2). The skeleton is composed of thin tubes, or pipes, (hence its common name), which are two millimetres in diameter and cemented together by horizontal plates at intervals of several centimetres (3). Unless the colony has been damaged, a mass of greenish-brown or grey polyps, each with eight tentacles, obscures the skeleton (2) (4). These colonies can form mounds up to 50 centimetres in diameter and may dominate large patches of reef (3). There are at least two species, only one of which is named; Tubipora musica (2). The structure of the tentacles of different colonies of T. musica varies greatly; some have broad feather-like pinnae (tiny projections) down the sides of the tentacles, whilst others have no pinnae at all (2)."