Hi,
I've just started using Pd, and my first project is to make some rhythmic patterns.
I'd like to start with a maracas type of sound, but don't want to start from scratch if I don't have to.

My thought on how to model this would start with:

• Generate N randomly delayed bursts of noise signal, sort of one for each bean.
  and then work from there adding filters and/or reverb to shape the sound.

Can anyone point me in the right direction?

You probably want to look into the Karplus-Strong algorithm;
I suspect that getting it to sound more like a piano than a synth will lie in getting the inharmonicities (sic?) right; I'm curious if anyone else here has looked into that.

Check if jack is running on your system.

I was seeing it (Ubuntu Studio 12.4), looking for a solution is what got me to this thread. I turned on the jack media and it went away. Somehow jack is auto starting for me (I used to have to start it manually).

Maybe not the best solution, but I'm using Ubuntu Studio, and it seems to work OK. Maybe looking into how to enable the packages related to studio might be helpful.