This piece has gone through several incarnations over its lifetime. When Leonard first composed it he called it 'Midnight on the Newport Cliffs', then 'Minuit sur la falaise de Newport'. Doris Day heard it, was impressed by it, and asked that this piece be used in her 1956 film, 'Julie'. The final version became known simply as 'Midnight on the Cliffs'.
Here is a brief MP3 sample from the 'commercial' version. MSR classics have included a live performance by Leonard from 1942, the earliest one available.
The following is taken from the liner notes of the LP, 'The Two Piano's of Leonard Pennario'.
One evening, in his teens, he was visiting friends who owned an atrocious piano, which was in addition, badly out of tune. They nevertheless insisted that he play for them. Feeling prankish, he went to the piano and improvised in march rhythm on the first tune that came into his head. His hostess remarked, "Only lunatics could march to that." Later that night, after he had returned to his home, Pennario wrote down his improvisation -- only to discover that each hand was in a different key, adding to the confusion!.
This piece was used as the theme music for one of the segments of the Saturday Night Live TV show. Leonard was very surprised when he got the royalty cheque!
Here is the cover, and here is the first page of this music.
When he was (only!) 17, while attending the University of Southern California, Leonard studied composition with Ernst Toch. When he submitted this piece his teacher's reaction was, "Very impressive but you are the only one who could play these."
His family recorded Leonard playing this in 1942; in 2004 while helping Leonard move from LA to San Diego, I discovered this recording, had it cleaned up, restored, and digitized.
This 
is a picture of the home recording after 50 years of sitting in the closet.
And here is the same disc after it was cleaned up.
Amazingly the audio quality was good enough that, in 2006, Leonard agreed to have it included as part of the "Early Years" 4 CD set. No one had heard it for over 50 years.
Sadly there is no trace of the actual music itself.
Here is an audio MP3 sample from that long lost private recording made in 1942.
Leonard Pennario has always been an unabashed movie enthusiast. In LA, even as a teen-ager, when he and his friends would go to movies, Leonard would go home and replay the sound track on the piano. Then he would begin improvising. The CD released in 1993, Film Themes and Variations, is a collection of themes from 11 films, with variations composed and performed by Leonard Pennario. Of course 11 barely scratches the surface, but it is all there is.