I can read music, which is like another language. Spanish, French or Arabic would be the only other languages apart from the English language, that would be worth learning. The rest are meaningless.
Sheet music doesn't have grammar or anything. It's just a basic written language for notes and tempo etc... Like mathematics, it doesn't count here.
Why is spanish worth knowing? Because a large part of the third world, latin america etc, speaks variations of it which sound like crap. It might be useful for backpackers haggling with filthy indians in Peru, but other than that I don't see why spanish would be useful. The people who speak it are mostly subhumans. If you switch spanish for chinese/mandarin, I can accept it. China is, unlike latin america, influential in the world and it's good to be able to communicate with them. I can understand quite a few of their writing symbols, through my japanese kanji studies, but I don't understand the language.
As for arabic, the arab nations will soon reach complete economic decline when the oil runs out. They don't even have their own infrastructures or resources to maintain it in the long run. They buy everything for oil money. Only reason to learn arabic is because of Islam. I'm not surprised though, a fuckfaced brit making such a politically correct comment.
The civilized languages, of civilized industrial people, include german, japanese, french, chinese, italian.
Swedish and dutch are closely related to german and most swedes learn german fluently after living one year in a german speaking country. Swedes and dutch can almost read each other's newspapers if they know a little german which helps tie the languages together. So, swedish is not completely worthless in the sense that it makes learning german way easier.