It's an explanation and not an argument. "Although it is an unusual song" is an assertion, an argument would say "therefore", or "that makes it", or some other phrasing that suggests that the conclusion that it is an unusual song follows from something else he has said.

Thank you for taking the time to answer me. I understand what you said, but what about the reasons after the colon(:)? Are just reasons used to explain why it's unusual?

Oh, shit... hmm... I didn't read it that carefully, he does seem to be suggesting that those reasons make the song unusual... I didn't notice that it was a colon...

I'm not sure either now, hopefully someone more logical, less intuitive comes along.

It's an explanation. He lists characteristics of the song that he believes are causes of him liking it, rather than reasons for him to (choose to) like it.

The word "reason" and the word "why" are ambiguous this way: you can ask why I'm voting libertarian, what my reasons are; and you can ask why the door is stuck, what the cause of its being stuck is, and you might also call that the "reason" it's stuck.

I think your textbook wants you to see these reasons as explanation-type rather than argument-type because it has thrown in some subjective stuff, like the solo being lovely, that's dependent on the speaker and you couldn't expect anyone else would consider them reasons.

I'm doing research now, more for me, so that I have a clearer cognitive grasp, but I think that my intuition was correct. http://csus.edu/indiv/m/mayesgr/phl4/because/part5argumentexplanation.htm

According to what I'm reading, the difference is more subtle than I realized, but I figured that in an argument reasons come before the conclusion, whereas in an explanation the reasons come after the fact.

Or it goes, reasons, claim, or fact, causes. So, just because of the order of it, I think that supports my intuition that is is an explanation. It's actually interesting how it is ordered, and I like the example differentiating evidence from causes, and highlighting the order with "smoke is evidence of fire, because fire causes smoke". So that in an explanation, the fact comes before the cause, whereas in an argument, the evidence is presented before the conclusion.

It also has a sense of an assertion "although it is an unusual song", this is presented as a fact, and the information after it is presented as the causes of that fact, so I'm sticking with explanation.

, Thank you both. I have been thinking that as Srap said, sometimes the words 'reason' and 'why' are ambiguous. So you have to look at the context and the intention of the speaker.

Also the example of evidences in arguments it's very clear. But, I came across with another text which has the same structure than the one before:

225 million women do not use safe and effective contraceptive methods. This is explained by many reasons, including lack of access to information or sexual health services.The problem is not only of women: there is a marked lack of support from their partners or the societies in which they live.

It doesn't seem to give an evidence of the assertion The problem is not only of women?

''I like that song for many reasons, one of them is because people love it, although is a unusual song: it has a lot of humor changes, a lot of contrasts, arrangements... There is also a lovely saxophone solo.'' [The one who speaks in the text is a musician] — Dasein

Two main points:

1. I like that song

2. Is an unusual song

Point 1 and its reason (people love it) form an explanation because there's no issue re the author's likes and dislikes. The author doesn't have to prove that he likes something.

Point 2 and its reason (it has a lot of humor changes, a lot of contrasts, arrangements... There is also a lovely saxophone solo) form an argument because the author has to show or prove that the song is unusual.