The title's a little disingenuous here - I do indeed show how to display and scroll through track lyrics in Music player - but currently only Symbian-powered phones running 'Belle Refresh' can do this - it's expected that this Music player enhancement will be one of the changes for Belle FP2 for the current FP1 devices like the Nokia 808. But, assuming you've upgraded your N8, E7 or similar, and assuming you have some time on your hands, here's what to do...

1. Find a source of MP3 or AAC files with embedded lyrics - this isn't trivial, though you may find some music prepackaged like this. Essentially, the lyrics need to be plain text, embedded in the header of the binary music file. The easiest way to get going though is to use your desktop music manager of choice (in my case iTunes, the market leader, but you may well have another favourite) and edit the header ('Info) for a particular music file. 
2. In the appropriate 'Lyrics' pane or edit field, type in the words needed, with a simple 'enter'/CR keystroke between lines. Much of the time, you should be able to find the lyrics to your song online, so find these on the Internet in a desktop browser window and copy and paste the lyrics themselves directly into the track info pane in the music manager. Save the results.
    
   
     
3. Now sync or copy this music file (and any others you have been adding lyrics to) over to your Symbian smartphone's mass memory or memory card in the usual way. I usually connect up my phone in 'Mass storage' mode and then simply drag and drop music folders over, but you may have a semi-automated system in place.
4. Now start up Music player on your phone and 'Refresh the library' if it's not done (or offered) automatically, to find the new track(s).
5. Start playing one of these tracks and tap on the (three lines) menu icon. You should now be offered 'Show lyrics', as an alternative to showing any artwork for the track. Select this and you should be able to browse up and down the lyrics for your chosen track.
    
     
    
6. At any point, when you want to go back to the artwork, just tap on the menu again and choose 'Hide lyrics'.

This extra functionality is not something that was mentioned in any of Nokia's changelogs - I suspect the intention was not to mention it until it had also been added to the latest Belle FP1 devices too. Hey, that's life - it's here and it works and now you know how to take advantage of it too.

In truth, this is quite a lot of work just to get lyrics inside (and displayed for) your music files - the alternative (and probably better) approach in the short term is to use an application like TuneWiki, wherein lyrics are grabbed on an as-needed basis from online servers. However, I can only find TuneWiki now for the E7, comments welcome if you can find another download of a Belle-compatible version of this client.

(Thanks to @SymbianSuomi for the heads-up on the feature)