I no longer joint sound-board panels with the machine, ultimately the hand plane does a better job. Unlike the hand plane, the machine Jointer produces a series of little scoops, the frequency of which depends on the feed rate of the work. A dull machine also tends to crush the wood cells, rather than cutting through them, which can cause a poor glue joint. At least one manufacturer of pianos is still jointing sound-board panels this way.
In the first picture you can see the very simple jig, or shooting board, that I use for jointing thin boards. On some, more traditional shooting boards, there might be a wooden hook at one end to hold the work. My jig uses small C-clamps (see below).