Sally, I have a dx of 'probable MS, but they are waiting for me to have 'another serious neurological episode' before I get the full dx. I was very poorly last winter, but am generally not too bad at the moment, just short relapses and the odd strange episode, like yesterday's.
The percussive tapping thing sounds a bit like the beating I used to have daily when I was hospitalised with pneumonia as a child. Mum had to do it for a while after I was discharged as well, so she could show me how. Ds2 is very like me, they can never hear he has a infection until its too late, they usually only track it down eventually by tapping and listening for dull spots. (Of course they won't listen to me when I tell them they need to do this, so its inevitably the 3rd or 4th doc that susses it out. 
)
As a child, I was getting progressively more and more sick for months with the docs saying they couldn't find anything. Ended up being rushed to hospital where they said I was basically on my last legs, but they still couldn't track down the infection. In the end one very old school radiographer decided to try a clever and little used angle and there was my double pneumonia in all its glory. It was mycoplasmic pneumonia as well, which is usually mild and known as walking pneumonia because most people never even realise they have it.
I was extremely lucky they caught it and also that I didn't end up predisposed to chest infections. Unfortunately, ds2 is definitely pre-disposed since he was hospitalised when he was 4, the GPs have his notes red-flagged to see him as an emergency if there is any hint of a chest problem, yet they still refuse to treat him until they can 'hear it'. We saw the head of practice both times with this infection and he was shocked when he realised that he'd turned ds2 away 5 days before when he did actually have an infection. Ds had been spiking temps up to 39 degrees for at least 10 days by then.