Playing audio recordings in the old days could be hazardous to your health.

[sl8]

A 20 minute recording took over a mile of steel tape and weighed 21 pounds. Operation involved the risk of flying steel shrapnel. Tape speed was 60 inches per second, which is 32x faster than a standard compact cassette tape.

https://www.bbc.co.uk/ahistoryoftheworld/objects/hnj413KZQx2FKn6nCLnUJA

The BBC had no viable means of recording sound until 1930. Among the first recording machines was the Blattnerphone, designed by early British film maker Louis Blattner.

The device used 6mm steel tape to record a very basic audio signal - good enough for voice but not for music. Spools were large and heavy, editing was done by soldering the tape, and the high speed at which the machine ran (5 ft per second) meant it was hazardous for the operator - a break in the tape could result in razor-edged steel flying around the studio

https://www.orbem.co.uk/tapes/blattner.htm

[...]

In September 1930 a machine was installed for trials at Avenue House, then the home of the BBC's Research Department and the results were deemed good enough for speech, but not for music. The BBC negotiated a five-year rental agreement with the British Blattnerphone Company in January 1931 at £500 for the first year, £1000 per year thereafter, plus £250 for each additional machine.

In May 1931 the Blattnerphone was moved to Savoy Hill (right) and entered service. In March the following year it was moved again, this time to the newly constructed Broadcasting House where it was installed on the seventh floor. A second machine soon joined it, allowing recordings of any length to be made by switching between the two recorders. These first machines were made in Germany. They recorded onto 6mm wide steel tape which ran at 5ft/sec. A full spool weighing 21lbs contained just over a mile of tape giving a recording time of twenty minutes. The speed of the D.C. motor had to be controlled by watching a stroboscope attached to the capstan and operating a sliding rheostat. The machines soon proved to be mechanically unreliable. In September 1932 a third machine was installed at BH. Again of German manufacture it used 3mm wide tape which came on spools allowing 32 minutes recording time. The drive was by an A.C. motor. With careful adjustment this machine gave better results than its predecessors, but still suffered from uneven tape speed.

[...]

Much more at link.

to No Such Thing as a Fish

[wcmagumba]

1. Wow, that was dangerous...I remember getting a small finger cut from a reel to reel tape years ago, not really...

[George McGovern]

2. Fascinating sl8. Thank You.