"He plays loudly."
Translation:Lui suona forte.
Hello! "Forte" in Italian can be either an adjective or a verb. That is, they are modal adverbs. I could not find a reference in English, but this is the Italian one: http://www.treccani.it/enciclopedia/avverbi-di-modo_(La-grammatica-italiana)/
Hello. "Rumorosamente" is more precise in its meaning, and it means that the sound level was high. Its closest translation in English would be 'noisily'. "Forte" is less specific, and it would be generally understood - by an Italian - 'loudly'. Please, note that the Italian 'forte' can be either adjective (loud) or adverb (loudly).