I don't know anything about Yahooooooo moooosic but if i were you, I'd try to download: http://www.flip4mac.com/ and see if this work. I have tried for video and it worked great.
Edit: The rumor is that Microsoft *possibly* stopped making Windows Media Player for mac and told the 3rd party developer to start makin' one. I don't know. That's how IE were dead.
LyFox works under PPC, you can try to see if it will work under rosetta, assuming that Flip4Mac works under rosetta as well. The program basically lets you search Yahoo Music and grab the videos.