All systems have their good and bad points. See Types of Accordions and How they Work for more detailed information. This is achieved by removing weight from either the tip or the base of the reed. There is no 'fixed' amount of higher or lower tuning to achieve musette. Accordions are manufactured in many countries.
Most production takes place in Italy, Austria, Germany, France, Russia, Czechoslovakia and China.
Some small production is from the USA and other countries, primarily using Italian or German components and assembling them. The number of manufacturers fluctuates all the time. At one stage, manufacturers in Germany and Italy were making approximately 750,000 instruments per year. There have been countless composers for the accordion. Some of the most famous are Piazzolla, Diero, Frosini, Chaikon, Molinari, Zolatariew.