The Mellotron Group

Hi all, I'm in the process of calibrating my SMS4 card and am at the 
point of tuning.  DK's instructions suggest tuning A to 440, and I hope 
this doesn't sound too stupid, but which A are we talking about?  I 
assume it's the low A on the keyboard.  Also, I have cello, three 
violins, and 8 voice in my frame - which would be the best (most stable) 
for tuning?  I've been trying to use an old korg guitar tuner, and it 
pretty much bouces all over the place.  I was thinking of tuning by ear 
to a sample played off my computer?  Any thoughts?
johnb
1407