I am so confused right now... I totally understand 'tengo sed' and 'tengo hambre' that's like saying 'I have thirst' or 'I have hunger'. I do NOT understand this one! It seems to say 'I have to win of to listen to music'... huh?!? How do you get 'I feel like' out of that?!?
I would encourage you not to be concerned with seeking to understand expressions in other languages based on their word-for-word equivalents in English. Even when you correctly identify the constituent elements, such a method will often fail to resolve confusion (a case I think also encountered here) and probably won't much help you commit the structures to memory.
OK, what are the constituent elements here? This isn't "ganas" as in the 2nd person singular form of "ganar." It's the plural form of the noun "gana," meaning "desire to do something." Wiktionary DRAE (which usefully lists a slew of other expressions using this term and notes it's "used more in the plural with the same meaning as the singular")
The "de" is where the first paragraph really comes into play. I don't think English usage is going to allow one to conjure up a natural analogue to it. If one looks at other Spanish expressions, however, it may seem natural. For instance one can say "sed de victoria" ("thirst for victory") or "hambre de descubrir la verdad" ("hunger to uncover the truth").
The expression "Tener ganas de + infinitive" means "to feel like (doing something)"
The last time I saw this question the answer said "I really feel like listening to music. Nobody I know says they are "keen" to listen to music.
I think "really feel like" -> tengo muchas ganas.
If the answer you submit isn't accepted, it just selects one that is currently accepted to show you. The fact you mightn't often say "keen" here doesn't mean it's wrong.
My problem with the translation is that I have seen variously: "I'm keen on listening to music", "I'm eager to listen to music" and "I feel like listening to music.". The last of those three means something completely different to me than the first two, certainly neither 'keen' nor 'eager'. Can a native Spanish speaker clear up the ambiguity here?
Not a native Spanish speaker, but maybe the following will be helpful: http://context.reverso.net/translation/spanish-english/tengo+ganas+de#
Note the presence of "I'm anxious to" as a translation for "tengo ganas de." "I'm anxious to" sounds pretty similar to "I'm eager to." "I"m keen on" sounds more different to me, too, but this could be an English dialect thing more than anything about Spanish. Or it could be confusing "keen on" with "keen to," which to me sounds largely interchangeable with the other expressions.
"ganas de" actually does appear as a listing for "keen on," but most of the sentences are in the negative, which switches things around a bit "http://context.reverso.net/translation/english-spanish/keen+on#ganas+de
If it helps, ganas = desire. http://www.spanishdict.com/translate/ganas
Thus, you're saying: I have (tengo) the desire (ganas) to (de) listen to (escuchar) music (música).
Another example: Si tengo ganas de trabajar, lo puedo hacer en tres horas.
If I have the desire to work, I can do it in three hours.
You just have to remember the basic formula: Tener (conjugate) ganas de + infinitive verb. This just gives you another way of saying that you want to do something besides using "querer."
This website is helpful if you want to learn more: http://worldspanishteacher.com/spanish-phrases-and-idioms/tener-ganas-de.htm#.W5xPN5NKjfY