Whilst practising this last night, a thought struck me. Few of the phrases in this seem to fall under my fingers. It's like I have to read absolutely every note. There's no short cuts, like where you recognise a scale or arpeggio that you've practised hundreds of times already and so is there "in the toolbox" ready to use. In fact there's hardly any phrases that are purely chromatic, or regular scales. Lots of the phrases use the interval of a fourth extensively. (Or sometimes a downward fourth changes into an upward fifth). I then realised that I've never actually practised any exercises based around fourths. Most of the studies I do are scale-based - so start on the tonic, up a third down a second up a third, and so on. Or up two semitones down a semitone, etc. These crab-wise scales are OK, but I'm going to have to add fourths to the mix too. Maybe Isaiah will seem a bit easier then.