First, read the English article below.

There is at least one for every note in the scale—and the savvy student will see that in some cases, there are two keys for the same note. For example, the key of G♯ sounds exactly the same as the key of A♭! When playing the piano—and for the purposes of this article, the difference is academic. However, there are some composers—especially those that write for strings—who will suggest that the A♭ is played a little "flatter" than the G♯. Here are the key signatures for the major scales:  Keys not using sharps or flats: C Keys using sharps: G, D, A, E, B, F♯, C♯ Keys using flats: F, B♭, E♭, A♭, D♭, G♭, C♭ As you can see above, as you move through the sharp key signatures, you add sharps one at a time until every note is played sharp in the key of C♯. As you move through the flat key signatures, you add flats until every note is played flat in the key of C♭. It may be of some comfort to know that composers usually write in key signatures that are comfortable for the player to read. D major is a very common key for string instruments to play because the open strings are closely related to the tonic, D. There are few works out there that have strings play in E♭ minor, or brass playing E major - it's as much a pain for them to write as it is for you to read. 

Now, please write a short abstract for it in Vietnamese. Abstract:
Hãy học các âm giai này.