You're quite right, Alexandre. Music is an uncountable or mass noun so we cannot say a music or even a beautiful music. Instead we have to use some or any or, if we want to refer to a single piece of music, we must use a partitive construction such as a piece of:

• I'm going to play you some music by Chopin.
  
  
• Have you heard this piece of music that he composed in 1826?
  
  
• I don't think I've ever heard any music by Chopin.

Most uncountable nouns, although they refer to mass items or collections of things, take a singular verb:

• Doesn't music interest you then?
  
  
• The furniture that I saw in the department store was very expensive.
  
  
• The advice you gave me on how to study for the exam was very useful.

Even the names of school subjects and leisure activities as uncountable nouns ending in s are used mostly with singular verbs:

• Maths is often perceived as a difficult subject, though I would say physics is more demanding.
  
  
• Billiards is an indoor table game and is played with three balls, two white and one red.
  

Cake

Unlike music, cake can be used as an uncountable or a countable noun, depending on whether you are thinking of a mass of cake or an individual cake:

• I'm going to bake a chocolate cake this afternoon and then, when it's ready, you'll be able to have some.

potato / pepper / onion

There are similar differences with other food items, depending on whether you are thinking of them as mass or individual items. Compare the following:

• Have you got any salt and pepper to put on the dining table?
  
  
• I couldn't decide whether to buy a red pepper or a yellow pepper.
  
  
• Would you like some mashed potato? ~ No thanks, I'll just have a roast potato.
  
  
• Would you like any onion with your hot dog?
  
  
• I'm going to cut up an onion and mix it with the salad.
  

paper / glass / cloth / work

Sometimes the meaning changes more radically with use of the countable or uncountable form of the noun. Compare the following:

• I'm going to buy an evening paper so that I can see what's on tele tonight.
  
  
• Here's some paper for you to draw on.
  
  
• This lampshade is made of paper.
  
  
• I don't need to wear glasses. My eyesight is pretty good.
  
  
• If you have any wine, I'd like a glass of red wine, please.
  
  
• It's better to use kitchen utensils made of glass, not plastic.
  
  
• Have you got a damp cloth? I've split some red wine on the carpet.
  
  
• There was not enough cloth remaining to make a second suit.
  
  
• There was no doubt. It was a masterpiece, a work of art.
  
  
• I don't have any work next week, so, unless I get some, I shall take the week off.
  

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