"I do not like that music, but I like the violin."
Translation:Je n'aime pas cette musique, mais j'aime le violon.
"cet" you use when you would normally use "ce" but the next word starts with a vowel, and it would be awkward to pronounce without the "t": for example, instead of "ce objet", we write "cet objet". cette is the feminine, so we have "ce garçon" and "cette fille". I recommend: http://french.about.com/od/grammar/a/adjectives_demonstrative.htm http://french.about.com/od/grammar/a/indefinite-demonstrative-pronoun.htm