Just open the Spotify Web Player in your Chrome Browser, play a song that has Lyrics, open the Extension and translate the song into any language that is supported by the Google Translate API.
This project was born out my personal desire to learn a language using lyrics. I would offer it for free, but the Translation API that is doing all of the work is not. To pay my cloud bill, I need to charge you a little bit of money. All profits at the end of the year will be donated to non-profits that are trying to build bridges between cultures.
If you are a developer and would like to contribute to the project or run your own version of it locally and with your own Cloud Billing, feel free to do so. You can find the source code for the extension and this website on my Github.