Some hardware and software is capable of displaying song texts while mp3s are played (similar to karaoke but with the original music). Although pushing and promoting this technology would certainly make a very attractive bonus of online music stores, in practice there aren't any (1) 100% working and (2) commercially available implementations. This can mostly be put down to the fact that the copyrights to lyrics and music are held by different persons. Merging lyrics with songs on a large scale therefore takes a lot of legal preparation. I am sure that these matters will be dealt with in 5-10 years from now and customers will definitely enjoy the new product, but till then we have to stick with diy solutions. Here goes my collection of more info on this topic - btw this page once ranked no. 1 on google.com when searching for "synchronized lyrics".