Soul, funk and rock samples are easy... I don't have formal musical training, but you find the right key, figure out if the initial chord is major or minor, stack notes until it sounds right, experiment with chord voicing (switching the root note of the chord is key), and listen carefully for salient voicing.... for example, if its an E minor triad chord, and you hear a B note over everything else, try playing B E G (instead of E G B )
Same rules apply to jazz, but there is much less room for error.... unless its only 1 or 2 chords, you probably aren't figuring that shyt out
By the way, start with the most basic major/minor triads. C E and G = major and D F and A = minor. From there you can stack on extra notes... for them jazzy r&B chords, play d F A C E
This is assuming that you get your synthesizer in key