Spencer Drate also has some commentary on this, and I found a YouTube copy of the first RCA demo 45 mentioned in the text: 


45 RPM: A Visual History of the Seven-inch Record 
edited by Spencer Drate (ppg.8-10) 
[in Google Books] 




‪ RCA Victor's 1949 Preview of the World's First 45 rpm Records!‬ 
https://www.youtube.com/watch?v=ebRx7FN6vlc 




============== 
Randal Baier 
Eastern Michigan University 
Ypsilanti, Michigan 48197 
(734) 487-2520 
[log in to unmask] 
tweets @rbaier – skypes @ randalbaier 
“... do not all strange sounds thrill us as human till we have learned to refer them to their proper 
source?” -Thoreau, mss., Journal 9: 1854-1855 



I just realized that, inspite of the fact that it retired years ago, the 45rpm disc turned 65 this year; does anyone know when its birthday is?
d



March 31, 1949 was the kick-off day. according to this site:
http://www.history-of-rock.com/fortyfive_birth.htm

However Wikipedia says:
Unwilling to accept and license Columbia's system, in February 1949 RCA
Victor, in cooperation of its parent, the Radio Corporation of America,
released the first 45 rpm single, 7 inches in diameter with a large center
hole. The 45 rpm player included a changing mechanism that allowed multiple
disks to be stacked, much as a conventional changer handled 78s. The short
playing time of a single 45 rpm side meant that long works, such as
symphonies, had to be released on multiple 45s instead of a single LP, but
RCA claimed that the new high-speed changer rendered side breaks so brief
as to be inaudible or inconsequential. Early 45 rpm records were made from
either vinyl or polystyrene <http://en.wikipedia.org/wiki/Polystyrene>.[34]
<http://en.wikipedia.org/wiki/Gramophone_record#cite_note-35> They had a
playing time of eight minutes.[35]
<http://en.wikipedia.org/wiki/Gramophone_record#cite_note-Williams-36>

http://en.wikipedia.org/wiki/Gramophone_record#New_sizes_and_materials

So On March 31, 1949, RCA Victor released "Texarkana Baby" b/w "Bouquet of
Roses" by Eddy Arnold.
http://www.recordcollectorsguild.org/index.php?name=Sections&req=viewarticle&artid=72&page=1