I forwarded Kevin's e-mail to John Gilbert, Herschel's son and here is his answer.....Interesting that you mention Yancy Derringer.  I haven't heard anything about that show in years.  I wasn't aware that the music was used for this show.  Knowing  this however, I'm assuming that it was a FOUR STAR production since my father was music director there and occasionally recycled his film scores for other purposes.  Others also did this with music from OPEN SECRET, which was used in dozens if not hundreds of episodes of SUPERMAN, RAWHIDE, TARZAN and even LEAVE IT TO BEAVER in the early 1950s.  The piece of music you are referring to came from the 1956 film called THE NAKED HILLS (aka THE FOUR SEASONS) with David Wayne, James Barton, and Keenan Wynn.  My father composed the score for this film and used its music extensively in numerous Rifleman episodes.  You can sometimes find it on EBay or in a video store that specializes in old movies.  My father mined his film scores for cues to use in the Rifleman and I have heard cues from perhaps a dozen or so films interspersed occasionally into Rifleman episodes for a particular effect.  I hope this helps.