Here is some text from the author that may help some in using
Iambic. - Bill W2CQ
"4 years ago, I made an on-the-fly YouTube video holding my phone in my left
hand to record the video while demonstrating the difference between
keying a paddle using iambic B and non-iambic (al'a single lever
paddle style). The video has had over 20K(100,000) views at
this point. So, if someone wants to see the difference and what
letters you can key iambic, take a look here: https://youtu.be/CVnTMsqFBzg
There are 7 letters you can key squeezing on an iambic paddle. ~27%
of the 26-letter alphabet. (The video shows the most popular iambic
mode B which usually is the default these days on any Keyer). The
"Iambic Seven" letters are C, Q, K, R, L, F and Y. As others have
mentioned and the video shows, you can simply use the paddle with or
without squeezing keying those letters. If you are going try and
learn iambic keying, I would stick with mode B, due to it being
pretty standard these days. i.e. if you operate and someone else's
shack."
A Great Demonstration of Iambic A and B keying for the beginner...
Beginning Morse Code -- Iambic Keying - AA4OO(previous
call) and now NG7M