random within random array?

Okay, now I've got myself lost. Awhile back I posted a message needing help with random characters. Michael Egan (thanks Michael!)was kind enough to send me his code, and others always gave snippets of info. I modified it to what I needed, and it worked great. However, now I am trying to figure something out additional to it. Basically, I need to generate 50 groups of characters. Each group will be made up of 3 different random (sets of) characters. the first set will be random characters from this group: a, b, c, d, e, f, g the second random from this group: es, is, null and the third from this group: null, ', '', ''' (yes those are single quotes) together, I want something like this: ces' c'' a''' gis'' bes fis''' and so on.. I'm sure this seems strange, but if you use Lilypond you probably know what it's for. Anyhow, if I can get any additional pointers that would be great. I don't want to seem like I'm asking everything to be written for me, but I just don't seem to have the programming mindset for things like this. Thank you in advance! Bryan