Why wa in Karaoke wa suki desu ka?


I recently came across an example in a text book

[code]

     カラオケは好きですか。
    
[/code]

and was not sure why `wa` was used here instead of `ga`?




> > カラオケは好きですか。
>
> why wa was used here instead of ga?

は is good for talking about _general idea_ , and this is the one to present
the subject/theme of the sentence.  
が usually introduces a happening, or is good at indicating the subject/theme
of _modifying clauses_.

In Japanese, the action maker is often omitted (because often the verb, or the
context, tells who or what is the action maker), but one of the basic sentence
structures is

**～は、～が～です。**

田中さんは、カラオケ **は** お好きですか。[a question about a general preference / we could have
plural subjects/themes (田中さんは and カラオケは)]

あ、田中さんはカラオケ **が** お好きなんですね。[a remark after finding out the fact]

はい、カラオケは好きです。[a statement about a general preference]

はい、そうなんです。カラオケが好きなんです。[could sound like after having a trouble mixed up as
though something else is your preference]

はい、そうなんです。カラオケは好きなんです。[after having a trouble mixed up as though you don't
like karaoke]




は is a topic maker, and it can _replace_ some particles including が. Here,
カラオケ is the main topic of the sentence, and that's why it's marked with は
instead of が. See [this
answer](https://japanese.stackexchange.com/a/17574/5010) for details.

カラオケ would be marked with が in the following two types of situations:

  1. When there is a different topic in the main clause: 

> 彼 **は** カラオケ **が** 好きですか。 (Here 彼 is the topic)  
>  Does he like _karaoke_?

  2. When this part is inside a [relative clause](https://japanese.stackexchange.com/a/14550/5010) (because a relative clause is just a modifier and does not serve as the topic of the whole sentence): 

> カラオケ **が** 好きな人 **は** 多い。  
>  There are many people who like _karaoke_.

