Each city works it differently, and, for example, Zurich (sober banking city that it is) has a relatively restrained one. Basel, however, really goes to town.
The organisation (and this is Switzerland, so it has to be organised) in Basel is based round the idea of the 'Clique'. A Clique is a club, usually associated with some workplace, or bar, or similar, whose sole purpose is to take part in the Fasnacht parades. Some Cliques are new, some go back over two hundred years, and there are probably a couple of hundred of them, ranging in size from less than a dozen up to several score. A Clique spends the year gathering money, because they need
b) masks (which cover the whole head)
c) a Laderna (Lantern) or float
b) instruments to play
The masks and costumes will be designed around a theme, or 'Sujet', which changes each year. As a for instance, a year or two back, when the Queen Mum was celebrating her centenary, there were several cliques who used her as a theme, including one where all the members were dressed as her, complete with hats that had gin bottles, corgis and the like on. Not all the costumes for a Clique are necessarily identical, but they are consistent - a Clique style, you might say.
Also, running along the same theme will be either the Laderne (usually a slab shaped, canvas-covered object, illuminated from inside so that the Hogarthian cartoons painted on the outside surface glow in the darkness) or the float. If it's a float, then it will usually be drawn by a tractor (suitably disguised and hidden) and manned by half a dozen or so maniacs who throw confetti (known locally as Rappli) and fruit and sweets into the crowds.
(We're not talking small ounce boxes of confetti, here. No, these guys buy it by the ten kilo bag, and frequently fire it using an air cannon. By the end of the day, the streets throughout the centre on the city look as though there's been a blizzard, and drifts of the stuff pile up.)
And they need instruments. Apart from the guys manning a float or pulling/carrying one of the Laderne, everyone plays an instrument. This is either a drum or piccolo (the traditional Swiss mercenary-style marching group) or it's a brass instrument (the Gugge bands). The treatment of the brass instruments in particular is far from reverent - they'll usually be painted in the Clique's colours and will often have extra decoration, and even LEDs stuffed down their throats. Yet these aren't battered second-hand items - they'll be the best they can buy.