Quiet, Please! (1947-1949, written and directed by Wyllis Cooper and narrated by Ernest Chappel, was an OTR drama series often noted as the most creative radio drama series in history for its surrealistic yet immersive quality, its depth of characterization, and its challenge to the traditional formula of entertainment.
Compared with other radio drama series, Quiet, Please! used fewer sound effects and less dialogue. Following the lead of Chappell's introduction, each episode was frequently punctuated with long, silent pauses, or innovative utilization of organ music (played by Albert Berman on most episodes). The result was a sparse, understated, often languid tone that demonstrates the narrative power of silence to evoke suspense and horror in a way unmatched by sound effects.
The stream of consciousness narrative, written by Cooper and spoken by Chappell, examined a world convincingly similar to that of the listeners, but not quite real, touched in some way by the supernatural, fantasy, horror, or suspense. Frequently, the dream-like, surreal quality of this world, complete with odd or paranormal events, was not explained. Cooper's experiments with stream of consciousness and first person narration were incorporated widely in radio drama years later. 
Quiet, Please! was created at WOR radio in New York City, and broadcast 8 June 1947-13 September 1948 via the Mutual Broadcasting System (MBS) and after that until 25 June 1949 via the American Broadcast Corporation (ABC).
Each episode was written by Wyllis Oswald Cooper (1899-1955), creator of the popular horror series Lights Out in 1934. Cooper went on to write and direct the crime series Whitehall 1212, 1951-1952.  Ernest Chappell, described in the credits as "the man who spoke to you," was the host and star.
Chappell, a former newsman and announcer (he was the announcer for The Campbell Playhouse, spoke slowly, calmly, directly to the audience in a quiet, conversational tone, befitting the character he portrayed. Chappell usually narrated each episode in first person, sometimes in present tense, and often in flashbacks. New characters (usually no more than three) were introduced without dialog, leaving each listener to fill in the details for herself. This gave listeners an immersive role in the unfolding drama.
Each episode began with Chappell intoning the show's title twice, with a long pause between. "Quiet please . . . Quiet please . . ."
After a dirge-like organ and piano rendition of the second movement of César Franck's 1899 Symphony in D Minor, Chappell began his first person narration. Here is a sample, from "Clarissa" (Episode 46; 19 April 1948).
No, he was dead before the fire started, I've told you that a dozen times! No, I can't prove it, of course not. You'll just have to believe me, take my word for it. I can't prove he was dead, you can't prove he wasn't! Anyway, what difference does it make . . . now? I'm sorry, I, I can't hear you very well. Yes, well, alright . . .
It was an old black shell of a house. A house that has lived too long. A house where the floors groaned in pain at night and windows shuttered at the gentlest touch of the wind. The door latches suddenly gave up their grip and let the night come snipping into the house to paw at your eyes and wake you to the other silences that lay around you. It was never warm there. In the winter old Heinz kept a fire going in the fireplace in the old sitting room, but the logs were scrawny and the draft was bad. And the flames seemed to grudge us their warmth so that we shivered all through the day. We were glad when night came and we could escape to the meager comfort of the drafty bedrooms. And in the summer, there was a dampness about the place. An unhealthy clamminess drifted from the walls and stirred uneasily among the ancient smells of decay that clung to the place . . .
A sense of indescribable emotion concluded each episode. Franck's Symphony in D Minor faded up, and then down into the background. Chappell provided the credits, and introduced the writer/director, Wyllis Cooper, who provided an often ad-libbed teaser for the next week's episode. Chappell provided a consistent closing. Again, from the episode "Clarissa."
I lifted him to the bed. I bent over him, I listened for his heart. There was no sound. Heinz was dead. Yes, just as I told you before, he died, there in my room, yes. What? Oh, yes. In the little half light, I found the kerosene lamp and I lit it. I took the key from the floor where he dropped it. No, I found the room very easily. It was at the far end of the hall. I called, 'Clarissa?... Clarissa?!' . . . and there was no answer. So I unlocked the door. And holding the light above my head I walked over to the bed. And there, lying on the bed, dressed in a pinafore that might have come out of a ten-year-old drawing of Alice in Wonderland, clutching a little woolly lamb to her breast . . . there lay a tiny, old, old woman with long white hair braided into pig tails . . . Clarissa. And I knew why I hadn't heard the little song for two days. And so when the lamp fell out of my hand and the flames started licking around the dry-as-dust draperies, and the fragile old oaken boards in the floor, I turned and went out of the house. (VOICE CRACKS.) For what else was there to do? The house had lived too long, and so had the father and daughter who dwelt there.
(Piano Music: 2nd Movement form Franck's Symphony in D Minor. Music fades into background.)
Quiet Please for tonight was called Clarissa. The man who spoke to you was Ernest Chappel. (Reads credits.) And now a word from our writer/ director, Wyllis Cooper.
The characters in tonight's Quiet Please are neither living nor dead. They enjoy neither of these interesting conditions because they are solely the invention of my own imagination intended to represent nobody at all. Quiet Please for next week is called "13 and 8."
And so until next week at this same time, I'm quietly yours, Ernest Chappel.
Cooper also wrote scripts for the NBC series Immortal Dramas, the third and fourth seasons of The Campbell Playhouse (29 November 1940-13 June 1941—formally the The Mercury Theatre on the Air which broadcast its last episode on 4 December 1938)—and Whitehall 1212 (1951-1952).
Episodes explored the supernatural, fantasy, horror, or suspense. Often listeners were introduced to a dream world where things were not as they seemed. Few happenings were explained or justified, they just happened. Many events had no reason or logic but were more terrifying than the gory stories and sound effects of Cooper's earlier Lights Out series.
Ernest Chappell was the star of Quiet, Please! Each episode was written for him.
Quiet, Please! website
Quiet, Please! Radio Logs at Jerry Haendiges Vintage Radio Logs website
Plot summaries and credits at Radio Gold Index website
OTRR certified episodes at Old Time Radio Researchers Library website
Single episodes at Internet Archive
The Definitive Quiet, Please! at Digital Deli Too website
Radio History of Quiet, Please! and Ernest Chappel at Radio Horror Hosts website
Total episodes: 106
Surviving episodes: 89 (approximate)
June 1947-13 September 1948
Mutual Broadcasting System (MBS)
continued until 25 June 1949
American Broadcast Corporation (ABC)
The Thing on the Fourble Board
Episode 60; 9 August 1948
Arguably, this is the most highly regarded episode of the Quiet, Please! series, which itself is often noted as the most creative radio drama series in history. Narrated by Ernest Chappel, who portrays an oilfield roughneck. He recounts a mysterious subterranean being, part human, part spider, brought to the surface by the oil drilling operation and hiding high up on the oil derrick. Richard J. Hand calls "The Thing on the Fourble Board" the finest example of both radio horror and radio drama as a whole. 
 Dunning, John. On the Air: The Encyclopedia of Old-Time Radio. (New York: Oxford University Press, 1998) 399-401.
 Hand, Richard J. "The Unsettling Universe of Wyllis Cooper and Ernest Chappell: Quiet, Please (1947-1949)" in Terror on the Air!: Horror Radio in America, 1931-1952. (Jefferson, NC: McFarland, 2006) 145-166.