Even if they made some noise, unlike many cassette recorders most reel to reel machines had no built in microphone fitted so an external mic it had to be and maybe just as well. Depending on the length of the lead you could keep some distance between the mic and a somewhat noisy recorder.
The early cassette recorders from Philips and others also had no built in mic. Built in mics came later as a convenience and mostly they were dreadful. Being so close to the mechanism, and mechanically coupled to it, they picked up every rattle, whirr and squeak, and only louder voices swamped this racket.
Some years ago we transferred thousands of hours of Oral History interview recordings on cassette. Many interviews were obviously recorded with the recorder's built in mic. Often the interview voices were close to inaudible. It seems many interviewers had not been given guidance as to suitable recording equipment and techniques. Such a shame as the interviews themselves were often of a very high standard with much preparation undertaken by the interviewers.
Interestingly, many of these cheap cassette recorders would have also carried a socket for an external mic but obviously it wasn't used. Maybe some users reasoned that since the inbuilt mics were a later development in cassette recorders, they must be "better" than the old external mics on a lead...
