Finally made it work, after keeping it aside for a month. The sense of long-lost, I-can-do-it pride, passion.
I was dealing with mingus — a client for Music Player Daemon from within GNU Emacs.. https://github.com/jialongl/mingus/blob/with-lyrics/ttlyrics.java
I just made a Java program to exploit the proprietary lyrics service from qianqian.com. Ya, call it a hack.
I Googled and found the hash algorithm in Java. So I just took it and added on. The plan is to make external call first and deal with lyrics rolling UI, finally translate the Java code to elisp.