Its been very interesting to read these messages. Eulalia, my 20-month son has exactly the same pattern of speech development that you describe for your son: Forgetting previously-learned words, in his case 'Oh dear' uttered around 14 months or so and now rarely heard, while also being a great sound imitator with very good manual dexterity. His shrill screems accompanied by much finger jabbing leave you in little doubt about his desires.
I'm so looking forward to him leaving the vocabulary starters gate. Croppy, glad to hear your son is making such progress.
My son says there, bear, mum, dada, good boy but not to order, and not that clearly either. But he instantly responds to soft music and loves drumming, so he can hear something!
I have already spoken to our health visitor to determine how long the current waiting list is for the speech therapist (3 months) and I will review things around this trigger age of two - and get his hearing checked.
I try not to compare my toddler with my older son - but I do. My older son talked very readly and extremely clearly from the age of 12 months. By the age of 2 years I had stopped counting the words he could say - it was well over 200. What's more, my early-talker son had mild but ongoing hearing problems for years,(diagnosed at nursery but probably present before this)and he just avoided having grommets fitted! Conversely, his manual dexterity was not that brilliant. To this day (he's nearly 7) he has never had any inclination to build a tower of bricks - one of those development landmarks he was meant to reach as a toddler.
As far as I know, I talk to my younger son in the same way as I did with my older son and I go through similar naming games that had positive effect the first time round. I definitely have the same sort of voice. Naturally my toddler is not getting my undivided attention, but because I am beginning to worry about his apparent disinterest in language, I'm trying all the more to get him to talk. For weeks I have been pointing my finger at every red bus we see and talking about them. He points with me and says his standby word 'there'. Same happens when we look at picture books. I can ask him where the dog is, and, if he's feeling like it, he points to the right picture but says 'there', not 'dog'. He also seems to like naming abstact things: when he's managed to get a particularly fiddly lid to fit a jar he'll utter 'good boy' to himself. Sorry, I'm ramblng. This is probably far more interesting to me than it is to anyone else!
Anyway, I have to admit one thing, much as I hate it. Because my toddler is not talking readily, and appears not to want to, it is affecting the way I bond with him - a very, very little. I love him to bits, but I want to feel my son seeks to communicate with me and the world at large, rather than being happily absorbed in his own. And talking is one of the tried and tested major ways of communicating. Selfish, I know, but there you go. I really hope I'll be posting news of his magical progress very soon.