Well, that was random

I've been playing Rock Band 2 recently - largely out of a curiosity.
That curiosity being: Just how random is the random feature?
And is there some way the user can somehow influence the song selection in the randomiser?
The last point may be unlikely but surely, once one gets a gold star on a song (the highest possible rating), they wouldn't have to do that song again?

Well lets find out:

Firstly lets establish my list of songs:

There are 80 songs from Rock Band 2
There are 63 songs from Rock Band 1
There are 45 songs from Lego Rock Band
There 50 songs from Green Day Rock Band (including 6 DLC)
And there are 163 Downloaded songs

This amounts to a total of 401 songs

Now earlier this month I started a new band career to test this theory out.

At time of writing, I'd amassed a star score of 684

• 274 stars were from 'set songs'
• 356 stars were from random setlists
• and 54 were from Make a Setlist
• This in turn breaks down to 55 songs, 72 songs and 11 songs respectively
• And three set songs have also been gold starred elsewhere

Now out of the 401 songs:

• One is a three star song
• 18 songs are four star songs
• 67 songs are five star songs
• 68 songs are gold star songs
• And 247 songs are unplayed

So if we assume I played every song once:
3 + (18*4) + (67*5) + (68*5)
3 + 72 + 335 + 340
 = 750

750 - 684 = 65 (rounding down to the nearest five)

This means 13 songs may have been duplicated.

Now, lets break down the song scores by game:

And finally there is my own personal experience: Whilst I may have so many songs in my RB music library that remembering when each and every one comes one may be near impossible, I do know of when I've had duplicates. And funnily enough, the majority of the ones I can remember came from RB2, ie Alex Chilton, Hello There, White Wedding and Livin' on a Prayer and that Winter song.
And yes, one such song was a song I'd already achieved a Gold Star for. 

So to conclude this incoherent rambling of mathematics, it would seem that the user has little to no influence on the songs selected at random. However whether or not Harmonix programmed something different is another matter entirely.
This is however only part way through the game: Insofar, I've done a lot of the Random Setlists and about one Make a Setlist (what you think I'm going to waste them?!). Needless to say, it would be interesting to keep up this experiment and see what happens in the near future...