abc2midi messes up with repeats in sections after a [1..[2 |] Jane found out that abc2midi output goes rather random sometimes. I've narrowed this down to sections of music after a [1..[2 |] repeat has happened. Work around by adding explicit |: for those sections, which doesn't (to my mind) look so good printed but gets correct behaviour from abc2midi.

\documentclass[a4paper,11pt,openany]{book}