The more important part in having fun playing this game is a good keyboard configuration.

Each player may have is favorite, but as for me I only completed the normal mode (and highers) after switching to :
- asd yuil (qwerty keyboard, more cramped because the ; can't be used)
- qsd uiom (azerty keyboard)
With no distinction between black&white keys, just assigning the keys from left to right.
It also make catching the golden notes not that difficult (it have some importance later on).

If you're left handed, you can use :
- zsdf jkl (qwerty)
-wsdf klm (azerty)
With some modification depending on your keys positions.

The thing is : putting your fingers on the right keys must feel near instinctive.

As stated by Ayelis in the coms, home row ([a/q]sdf jkl[m]) ARE instinctive if you're used to typing. As such a perfectly viable option.

When you're done, with just a little practice you should complete all the stages smiling.

So, now that you already have completed all stages from too easy to Chopin, what's next ?

Well, some hard-to-earn point-scoring achivements.

Basically, when trying to unlock the last one, "Grand composer", you should obtain the remaining few non-story non-difficulty related.

This one require some big score to unlock. The way to win points is already well explained in another great guide, so read it :p

When you're familiar with red notes, combo/golden notes and the sort, all you have to do is play your favorite stage on Chopin difficulty and try to score as big as you can.

The easier you can catch golden notes, the better.

Each stage have a different score to exceed, and if your favorite stage is too hard you can always play in Paris. In this stage you just need to score more than 40 000 points (before the difficulty bonus, which should make a final score of roughly 65 000 points) .
Child's play if you can chain red/blue combo.

Have fun playing, thanks for reading !