The pitch of the recording of Telón by the orchestra of Lucio Demare with singer, Juan Carlos Miranda (1938) drifts throughout the song. It’s a feature of the original recording (the rotating speed of the wax master must have varied, probably as a result of an irregular power supply to the motor).
As an experiment, I chopped the track into six segments of roughly equal length, measured and corrected the pitch of each section separately (tuning to A = 435 Hz) and then spliced them back together. The pitch difference between any adjacent segments is below the normal threshold for audibility (5 cents), and it is very hard to detect the joins. It only took ten minutes to do and was just for fun. Other people might have found something better to do with the time …
Here it is (as an MP3 file with a decent bitrate).
May-20: Here’s an alternate rendering (try it on headphones) in pseudo-stereo and with reduced mains hum. The sound is astonishingly good for 1938 – it almost sounds modern: