[3][4] He died during World War II, on 7 June 1942, aged 38, during the secret trial of an H2S airborne radar system then under development, when all on board the Halifax bomber in which he was flying were killed when it crashed at Welsh Bicknor in Herefordshire.

In 1929 Blumlein resigned from STC and joined the Columbia Graphophone Company, where he reported directly to general manager Isaac Shoenberg.

He invented the moving-coil disc cutting head, which not only got around the patent but offered greatly improved sound quality.

During the early 1930s Blumlein and Herbert Holman developed a series of moving-coil microphones, which were used in EMI recording studios and by the BBC at Alexandra Palace.

Blumlein discovered that if the tap was placed at a distance 15–20% down from the supply end of the output transformer, the tube or valve would combine the positive features of both the triode and the pentode design.

The sound reproduction systems of the early talkies only had a single set of speakers – the actor might be on one side of the screen, but the voice could come from the other.

His earliest notes on the subject are dated 25 September 1931, and his patent had the title "Improvements in and relating to Sound-transmission, Sound-recording and Sound-reproducing Systems".

Some 70 claims include: Blumlein's binaural experiments began in early 1933, and the first stereo discs were cut later the same year.

[9] In 1934, Blumlein recorded Mozart's Jupiter Symphony conducted by Sir Thomas Beecham at Abbey Road Studios in London using his vertical-lateral technique.

Blumlein's contributions, as a member of the EMI team, started in earnest in 1933 when his boss, Isaac Shoenberg, assigned him full-time to TV research.

His ideas included: Blumlein was also largely responsible for the development of the waveform structure used in the 405-line Marconi-EMI system – developed for the UK's BBC Television Service at Alexandra Palace, the world's first scheduled "high definition" (240 lines or better) television service – which was later adopted as the CCIR System A. Blumlein was so central to the development of the H2S airborne radar system (to aid bomb targeting), that after his death in June 1942, many believed that the project would fail.

Blumlein's role in the project was a closely guarded secret at the time and consequently only a brief announcement of his death was made some two years later, to avoid providing solace to Hitler.

During the flight from RAF Defford, whilst at an altitude of 500 ft (150 meters) the Halifax developed an engine fire which rapidly grew out of control.

The Halifax was carrying a highly-secret cavity magnetron as part of the H2S test system, and the immediate recovery of the device was essential.

[14] After the RAF investigative board completed its report on the Halifax crash on 1 July 1942, it was distributed to a restricted list of approved recipients, but not publicly divulged.

[10] With the loss of a substantial part of the starboard wing, all control over level flight was lost, and the plane rolled inverted and struck the ground at approximately 150 mph (240 kph).

[10] The board found that the crew and passengers had not jumped immediately from the aircraft owing to several factors, including a loss of altitude while attempting to find an emergency field, the rapidly spreading fire, which blocked or impeded egress from the plane, and the fact that a sufficient number of parachutes were either not on board or were not being worn.

[10] Almost immediately following the crash, Prime Minister Winston Churchill issued a directive requiring any test flights with civilians or scientific personnel to carry a sufficient number of parachutes for all individuals involved.