IT SEEMS IT ONLY CREATES 8 BARS MUSIC  , WHICH ARE REALLY FEW....(or I'm wrong ?)

A song is made up of blocks. A song can use up to 30 different blocks.

The blocks are shown at the top of the screen. To switch from one block to another, just click on a block.

Here is a tutorial that explains this part:

Oh , Thank you  for the clarification

will purchase immediately !