[DC] hears a faint counting voice in places, but says that it could be the mind playing tricks.
From start and throughout there is a slow lapping sound that seems to have been sampled or inspired by a soundtrack from 'Nature' (s6 ep13) "Hawaii: Islands of the Fire Goddess" (1988/02/14) [PBS (for BBC)] at 53:22 & 55:06.
"Corsair" could refer to a pirate, especially a privateer of the Barbary coast. Alternately, it could refer to any of several military aircraft, such as the Vought F4U Corsair.
[DC], after the first few listens, believes he could hear a voice; a child's voice counting as in Gyroscope (most strongly at 2'11, as follows: 2'11 "one", 2'13 "two", 2'15 "three, 2'17 "four" ...), almost as a sort of faint "echo" of sunshine recorder the start of the album. (Since writing that, another correspondent has expressed agreement that there is a voice here: that it sounds like a voice vocodered with a white noise source - which would produce just such a kind of "speaking static" - and then filtered).