Does music help you focus? It depends on the person, the task and the music. Some people work well with the TV on, but I am not among them. I find that music where I listen to the lyrics distracts me, but other music can help me focus on boring tasks. Which should be understood as "helps my concentration to be marginally less terrible" for those things. For interesting tasks I don't need music.
Music for which I don't listen to lyrics comes mostly in two types: classical music and (electronic) dance/trance (broadly). Many in the latter category are in fact vocal, but it is easy to ignore since you don't really miss anything (don't hate me please). This post is about classical music.
Classical music is all pretty old, so there shouldn't be any copyright, right? Yes and no. The "classical music" label is also applied to most any modern music that could be performed in a concert hall, but more importantly, there is a copyright on the composition and on the performance. Most recorded performances are fairly recent.
Musopen to the rescue! Musopen is a USA non-profit that collects music that is in the public domain. That is to say, it's probably in the public domain in the USA, without guarantee, and laws might be different where you live. Legal details aside (I'm not a lawyer), it's a very nice idea to have a music equivalent of what Project Gutenburg is for books (which seems to be the more famous initiative of the two).
Conveniently, there's a collection of quite some classical songs that Musopen raised money to buy and release into the public domain. Here! It's called the Musopen DVD, apparently DVDs still existed in 2012. You can just download a zipfile. There is a lossless version but I can't hear the difference. Either way, should give you some hours of focus!