I.on [美 ɑn, ɔn, 英 ɒn]介词on often appears as the second element of certain verb structures in English (count on, lay on, sign on, etc). For translations, see the relevant verb entry (count, lay, sign, etc).
Play was rough: players would pile on fallen players, walk on them, kick them, including in the face, pull on arms and legs and stuff dirt in each other's mouths.
After an average start, a run of 14 games without a win (and very few draws) saw us end up bottom of the pile on 31 points and automatically relegated.
It is a clever device which allows him to pile on the tension between anxiety (the solo recitative interjections) and belief (the choral delivery of the hymn stanzas).