Can you help me to choose
a niche topic?

Question - I seem to stuck at the site concept keyword. My first thought was to build a site about Classical Guitar - Specialize in its Technique.

Another theme I would like to do is Travel Singapore, which probably I can expand my monetize items to another SBI site Travel Asia.

Please give me your thoughts on these two ideas?

Answer - If you would like to build your site on Classical Guitar, it would be called something like www.classicalguitartips.com or www.specializedclassicalguitar.com or something like that (as long as it's available and not trademarked already).

If your brainstorming gives you a lot of tier two and three keywords for guitar, then this could be a good topic for you.

Don't worry about having your site rank well for the keywords Classical Guitar, it never will. As long as you have other keywords you can rank well for (according to the Brainstormer numbers) people will find you through these.

Always use two keywords and probably three as most of the good two word domain names are taken now.

Three words are still good so don't worry about having a long URL as long as it's on topic with your chosen niche concept.

The keywords you sent me -

2. Classical
3. Techniques
4. Travel
5. Singapore
and
6. Asia

...are all too generic so don't try anything in Brainstormer with these.

The words -

1. Classical Guitar
2. Travel Asia
3. Travel Singapore

...are perfect to start your brainstorming sessions.

All of these topics would make good niche markets as long as you can find other supporting keywords in Brainstormer.

One last thing, never put underscores in your domain name, and only use dashes if you absolutely have to, they aren't required any more as search engines can read the words these days.