"Catacombs" is a creepy, unsettling track. It features a string arpeggiated augmented triad ostinato from F which systematically peaks at D and descends back, as well as a rhythmical basis from a ride cymbal. Despite this ride cymbal, the song is generally arrhythmic, with several instruments playing out of sync with each other. The rhythm of the ostinato and ride cymbal implies a 6/8 time signature, and the song has a repetitive and circular nature that prevents it from becoming too unstructured.
Throughout the track, a variety of noises play, such as gongs and a droning bass choir, overriding one another and forming diminished harmonies. These eerie noises only ever cease halfway through the track and near the loop point. As the song nears the loop, a loud sequence of low bass choir and high string notes plays, briefly drawing attention to themselves. The song loops roughly 80 seconds in, with it being difficult to tell the exact point due to the song's circular and arrhythmic nature.
Several of the song's instruments — namely, the strings, bass choir, and ride cymbal — are later reused in "0² Battle". However, said song is significantly more melodic and structured, and does not resemble "Catacombs" beyond the instrument choices. Regardless, it may serve to foreshadow the musical style associated with 0², along with fitting the tense atmosphere of the Dark Matter-engulfed Ripple Star.
Kirby 64: The Crystal Shards
So far, "Catacombs" has only appeared in Kirby 64: The Crystal Shards, playing in Ripple Star - Stage 2. It is the 16th track in the Sound Test, and causes Kirby to gain a shocked expression when it plays. The track was not included on the official soundtrack release, Hoshi no Kirby 64 Original Soundtrack. As such, its official name and composer are unknown.