Opera Max now saves you up to 50% of the data used to stream music from certain sites

Besides saving data, the Opera Max app will also keep track of data usage over both cellular and Wi-Fi. This helps users see how much data they have consumed on a daily or monthly basis, so that they can have a better grip on their account. If you find yourself constantly exceeding your monthly data allowance, paying overages or getting throttled, this is an app that you need to install on your phone.
"More and more people love listening to their favorite music with apps; however, these apps are among the major data hogs consuming users’ mobile data quickly. Now, we have added audio compression for these music apps so that people will feel free to stream music without having to look constantly for available, free Wi-Fi coverage. This is particularly helpful for users with limited data plans."-Sergey Lossev, Product Manager, Opera Software
Opera Max is a free download from the Google Play Store, which you can install by clicking on this link.
source: Opera