Translation:My grandfather likes listening to Italian music.
Normally that is the case, especially with backward verbs like gustar where música italiana appears to be the subject.
However, upon closer inspection, the subject is technically escuchar música italiana---and música is the object of a preposition (an implied one, listening to), where the rule regarding definite articles for generalities is actually the opposite.
This is almost identical to the one just before where it marked my answer wrong because I did not put the 'la' before 'musica', then I had a info page come up to tell me why 'la' was required. Next one it is not required. There must be a rule that I am missing, your explanation above would seem to fit both.
There are regional differences with verb jugar. In some Spanish dialects jugar takes almost always 'al' or 'a la' when referring to practising sports. In some dialects they are left out like "jugar fútbol". Duolingo seems to prefer "jugar + a + definite article" so I would say in this particular case the jugar verb is special.
In this case, the 'le' means to him. the literal translation of gustar is "to be pleasing". By putting le in there, we make it "is pleasing to him", but in English, we equate it to "to like". Without the le, the sentence would translate to "My grandfather is pleasing to listen to Italian music." This gets extremely awkward when the sentence is "My grandfather likes kids." and it is translated wrong. "A mi abuelo gusta los niños" translates to (roughly) "My grandfather is pleasing the kids." (The silly examples are what helped me to remember this stuff even years later.) I hope this helps!
A few other verbs that require the (me, te, le, nos, les) are: faltar, encantar, importar, hacer falta, parecer, picar. You can look up the definitions of any of the words you do not know.
Source: I studied Spanish in school for ~10 years.
Fantastic explanation, I think I will be able to memorize it from now on. Btw, could you also tell why we put 'A' at the beginning? I was going through the directory when suddenly an A is given at the beginning of such sentences and I fail to grasp the concept when it is needed and when the subject of the sentence can go without an 'A' at the beginning.
The a at the beginning clarifies who likes it. It's used mostly with le (and les) because le just by itself could mean he/she/it or even you as in usted. For example, a él le gusta means "he likes it."
It also appears redundantly with me/te/nos as a mí /ti/nosotros for emphasis, usually in response to a question.
hope it helps https://studyspanish.com/grammar/lessons/gustar short: ''Le gusta la silla. It is impossible to tell whether this means: He likes the chair. She likes the chair. You (usted) like the chair. For purposes of clarification, the sentence will often begin with a prepositional phrase that clarifies just who the IO pronoun refers to. A él le gusta la silla. He likes the chair. A Juan le gusta la silla. John likes the chair. As you can see, by adding a prepositional phrase, we remove the ambiguity of the “le” form. You can also use a prepositional phrase to add emphasis, even if there is no ambiguity. A Juan le gusta el café. John likes coffee. A mí me gusta el té. I like tea. In the first example, “a Juan” clarifies the ambiguous pronoun “le.” In the second example, there is no ambiguity. “Me gusta el té” can only mean “I like tea.” In this case, “a mí” adds emphasis, drawing attention to the fact that tea is what I like (as contrasted with what Juan likes).'' quote
No, 'a' has no effect on the meaning. It's required because you're actually saying 'To my grandfather listening to music is pleasing', so you need to include 'a' as the translation of 'to'. The verb similar to 'gustar' which is usually translated 'to love' is 'encantar'.