When shooting round shot (massive iron cannonballs), the artillerymen would aim to make the cannonball skip or bounce, much akin to how you throw a flat stone on a lake, in order to do as much damage as possible and pass through as many enemy ranks as possible. The ball would be heavy, but velocity would be low compared to modern shells and get lower with each bounce. And yes, body parts would be flung around a lot by cannonballs impacting lines of men. This scene from 'The patriot' shows a bouncing cannonball quite well.

Focus was certainly to keep formation and not to stop to help wounded or take care of the dead until after the battle - in general, the unit that could keep discipline and formation was the one that would be victorious, and most casualties happened once one side had started running, so focus was always on keeping formation. Men replaced those that fell and kept the formation.

In the Swedish army, music/sound was provided by drummers and pipers (in the infantry), with the pipers replaced by hornplayers later in the 18th century, or drummers and trumpeters (in the cavalry). The pipers' main duty was to provide simple orders that could be heard wide and far through the sound of the battlefield. Roughly 30 different orders could be relayed this way and the soldiers were required to know and recognise them by heart. These included thinfs like attention to orders for the brigade, the regiment and the battalion, officers to the commanding officers for orders/planning, specific signals for specific part of the unit (right flank, left flank, centre, flag carriers) and specific orders (fire, charge, march forwards, march backwards, march right, march left, halt, fire, charge, form firing line, correction on the right flank, left flank or centre, advance double-quick) and so on. Roughly half of these commands could also be given with the drums, but the drums were mostly used to set the pace for the march and the charge, with one drumbeat for each step. The pipers and drummers could play music on the march to provide entertainment, but on the battlefield, they were strictly used to communicate orders. Drums, pipes, horns and trumpets were designed to have a tone quite different from the sharp cracks of musket fire or more thunderous sound of artillery to be heard over the sounds of the battlefield. Each part of the battalion had NCOs and lower officers responsible for their part of the battalion. When a piper sounds an order, they would hear it and ensure that the men under their responsibility obeyed, which could include yelled orders. In the Swedish army the drummers and pipers were deployed in the centre, behind the battalion.

NCOs, often equipped with halberds, were deployed at the rear ranks of the battalions and responsible for keeping the men in formation. In the Swedish army, a senior soldier were also responsible to make sure that the junior men kept their place in the formation during the march. Fire was often opened at about 100 paces, a range at which very few shots would hit, and depending on the school of infantry tactics used (Anglo-Dutch, French, Swedish, Austrian/High German or Russian), distance would be closed and fire become more effective. Harsh discipline was maintained at any time they could by the NCOs in the rear, and they were authorised to use leathal force againt anyone running from the battlefield, causing a weird dynamic where you did not want to be the first who ran and was prodded back or even killed by the NCOs, nor the last who would be cut down from behind by the advancing enemy. In general, the unit which fired at the shortest distance (which often meant last) and kept its formation better would do more damage - and this required discipline and training. Withholding fire and advancing in the face of enemy fire also showed that discipline and training, establishing a sense of superiority both in your own men and those of the enemy - making for psychological warfare.

No, not really. You were supposed to accept the surrender of men that did surrender and not take up arms again if you had surrendered. Most would attempt to care for the wounded of the enemy after caring for their own. Strange things could of course happen, like the Battle of Fountenoy 1745, where the British and French Royal Guards met on the battlefield, and both advanced without firing, showing thier discipline, until they were so close that the officers could adress each other, and at 30 paces, the British officer Lord Hai supposedly offered the French to shoot first (exactly what was said differs with the sources, but "Gentlemen of France, fire first!" is often quoted). Civilians observing the battle was rare, and the only occassion I can think of is the 1st Battle of Bull Run 1861, in the US Civil War.

Yes, soldiers were encouraged to keep quiet unless ordered to cheer or give up a war cry by their officers - discipline and being able to hear orders were important. And yes, the battlefield was probably way more chaotic than is shown in movies, with crying and yelling wounded men, NCOs and officers trying to make themselves heard over the sounds of dying men and horsers, musket salvos, the thunder of hooves and artillery fire.