The string bands are the only part I like and FWIW, /u/LePetitRenardRoux, probably the most distinctive kind of group to watch if you don't want to do the whole thing. (They're allowed to have wind and string instruments but no brass, so there are big ensembles of mainly saxophone and banjo players... it's a unique sound.) I usually start checking on TV at 11 but IIRC it's always massively late so I bet it could start well after 12. Also I've almost never bothered watching in person because the bands do their main performance at City Hall so unless you're willing to brave that crowd, it makes more sense to watch on TV.