The score is divided roughly into two categories as it was with all three Irwin Allen catastrophe movies, the source music styled pop-ish tuneful material and the sparse, steely, mournful and creepy dramatic underscore for the obstacles the characters have to overcome to survive and the tragedies that happen along the way. Although this one contains perhaps less of the pop tune sensibility than the two other disaster spectacles (there is half an album of source music here though) it is quite removed from Williams' more tuneful efforts really. The main title theme appears very sparsely, mostly to open and close the proceedings although I think it is a great one, full of turbulent foreboding.
Interesting comparison on the LLL album are the two alternate takes on the main title sequence which are dark, non-thematic, atmospheric and creepy, more avant garde than anything else on the disc.
In all honesty I do not find myself returning to this trio of scores too often (although I should listen to Poseidon more as I think it is a fine if subdued dramatic score), but I would place them in order as follows:
1) The Towering Inferno
2) The Poseidon Adventure