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As a medium of storing large data, cassette tapes were used just like the following:

TRS-80 cassette system

I wonder what it would sound like if one put the tape in a cassette player and played it as if it were a regular music cassette tape. Where can I find audio footage of that?

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    Does this answer your question? Cassette tape storage formats
    – pndc
    Commented Jan 15, 2023 at 19:05
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    @pndc This doesn’t seem related at all. Commented Jan 15, 2023 at 19:06
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    youtube.com/… the cassette output is played out loud Commented Jan 15, 2023 at 20:03
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    How the data played back would sound depends on which tape protocol the computer system used to store data, and it would also depend on what data is being stored. Typically storing ones continuously would sound different than storing zeroes continuously. As usable data is neither, it will be a complex mixture of timbre based on the stored data, as it is impossible to hear the individual pulses of each data bit separately. Which computer system you had in mind?
    – Justme
    Commented Jan 15, 2023 at 23:19
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    Boooooooooooooooooooooo-SCRACK! Boooooooooooooooo-ScraaAAaAaAAaAaAaAAAAAAAaAaAaAAaAaAAaAaAaAaAaAAaaAAaAack!
    – Muzer
    Commented Jan 16, 2023 at 13:38

8 Answers 8

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It sounds like a high-pitched noise, somewhat like you would hear from a modem. Here's a little TRS-80 Model 1 BASIC program that plots every pixel on the screen:

10 FORY=0TO47
20 FORX=0TO127
30 SET(X,Y)
40 NEXTX
50 NEXTY

When saved on a TRS-80 Model 1, Level 1 BASIC it sounds like this:

http://48k.ca/misc/set1.wav

That's 250 baud or 250 bits per second in this case. Saved under level 2 BASIC is sounds like this:

http://48k.ca/misc/set.wav

It runs at 500 baud so it sounds an octave higher. It also encodes the BASIC program a bit differently so the noise has changed.

The TRS-80 Model III can save at a blazing 1500 baud causing the program to sound like this:

http://48k.ca/misc/set3.wav

Besides the pitch change the bit encoding is different. Despite it sounding like noise you can hear how it is very easy to distinguish the 3 different formats by ear.

Notice also how they all start with a quite regular sound? That's the "header" which is used to get the computer into sync with the cassette bits when it loads them. It is quite long in order to give the cassette time to get up to speed when writing.

Having used cassettes on the TRS-80 back in the early 80's I can assure you we heard that sound a lot. You wouldn't in normal operation but curiosity and practical need had us listen to the tapes. Some times to hear if a program had drop-outs or other problems that would explain why it wouldn't load. Or to locate the start of a program on tape which has multiple file saved on it. Or to figure out what baud rate to set when loading the program.

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    The sound is long not just to "get the cassette up to speed", but also to account for the fact that many casette tapes had leaders on them which were incapable of recording audio. If computers started recording material that mattered as soon as someone hit "save", a user would have to first advance the tape just past the end of the leader.
    – supercat
    Commented Jan 15, 2023 at 20:44
  • The third one was gold! I really appreciate the footage. Commented Jan 16, 2023 at 1:24
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    That is totally the sound of the 80's... kids would obviously check the audio result of the tapes, and sometimes tapes got mixed up and the surprise beep would zap on the HiFi. Commented Jan 16, 2023 at 9:27
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    @LifeInTheTrees Or if you used a Spectrum, you actually had to use the line-out from a regular audio cassette player, so you would always hear it anyway.
    – Graham
    Commented Jan 16, 2023 at 11:38
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    This brings back memories of this coming up as a plotline in Murder She Wrote where a cassette tape was thought to have been corrupted, or damaged, because it was just noise, but instead turned out to be a program. I remember, when they played the "noise" on the show, immediately recognizing it as code. :) Commented Jan 16, 2023 at 13:51
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I understand this question is about the Tandy, so I'll move this to a self-answered question if necessary, but I believe you'd be interested in this information. On a ZX Spectrum (at least, the popular +2A revision with integrated Datacorder and modulated RF sound through the TV), the audio waveform on the tape is played through the TV's speakers during loading as various (unpleasant) sounds. ('Like a donkey drowning in something viscous.' it's been called.)

Because the different parts of a recorded block of data on a Spectrum tape have a uniform layout and timing, these phases not only had predictable colours on screen but also familiar tones - the result is a slowly cycling combination of constant tones, screeches and noise.

This video is the full loading of Jetpac for the Spectrum:

https://www.youtube.com/watch?v=V0EfycbDhiw

The 'pilot tone' is shown as red and cyan bars and sounds like a constant square wave. Block headers consist of a pilot tone followed by some data, so when a game begins to load, you'll hear 'beeeeep - squish' as the block is synced to then loaded.

The content of longer data blocks will have long random crunching sounds accompanied by blue and yellow dense bars as the data is loaded.

Periodic data will have its own characteristic periodic sounds while loading . This is particularly noticeable when the full content of the Spectrum screen is loaded directly -uncompressed- from the cassette into screen memory to display a title screen during the remainder of the loading process1. This memory block is sometimes called a SCREEN$ after the BASIC token representing it. A SCREEN$ has the 1bpp graphic INK data for the screen (in a non-intuitive layout of lines) first followed by the colour attribute values as a block. This means that a game title screen with a lot of repeating patterns in its graphic will have distinctive repeating whirrs, chirps, or crunches as the visual patterns are read. The attribute table also has its own unique sound since most of the screen will have repeating/common sections of colour.

Due to these effects, when a game is first loaded on a Spectrum, the initial load of the title screen has a very recognisable sequence:

  • boooop - bip - silence (loading and displaying the program name)
  • boooop - crunch - silence (loading the BASIC loader from the tape that will control the rest of the loading - the screen may go black at this point if the loader code chooses to do so)
  • boooop - cru-cru-cru-crunch - cru-cru-cru-crunch - cru-cru-cru-crunch (this process is lengthy as the picture dot data is loaded)

then finally

  • nya-nya-nya-nya-nyaaaaaaaaaa - silence (the attribute table is loaded and the title screen is 'coloured in')

Then the main game content and assets will be read as longer data blocks consisting of protracted (ten minutes upwards) continuous random harsh high pitched crunching sounds preceded by pilot beeps.

As Doc Brown would say 'Please excuse the crudity of this model.', but this is the best way I can convey it in words. :)

Further reading:

What should be the waveform for ZX Spectrum tapes?

1. You may have noticed that if it's loading directly from tape to screen memory, the Spectrum isn't doing anything else while the title screen loading is taking place. The game isn't loading in the background! A full one minute of loading is just to show a pretty picture before the real loading begins.

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    Yep : "Boooooooooooooooooooooo-SCRACK! Boooooooooooooooo-ScraaAAaAaAAaAaAaAAAAAAAaAaAaAAaAaAAaAaAaAaAaAAaaAAaAack!"
    – Mazura
    Commented Jan 17, 2023 at 2:05
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    Also worth reminiscing that for earlier Spectrums, such as the 48K one that we had, the tape recorder was just a normal portable audio tape recorder, which you connected using an audio cable. At least in our case you'd hear the loading sounds through the speaker built into the tape recorder. (Game sound effects would come from a speaker built into the Spectrum itself.)
    – N. Virgo
    Commented Jan 17, 2023 at 9:28
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    @N.Virgo On the earlier Spectrums, the tape loading noise came out of the internal speaker. I can't comment on your case, but most portable tape players would disconnect their speakers whenever a cable was plugged into the headphone socket, so all the loading sounds would be coming from the Spectrum itself. Commented Jan 17, 2023 at 14:13
  • Thanks Virgo + Alex. :) I've never used a slab-type original ZX, and in my experience tape players cut out the internal speaker when an aux lead is inserted, but of course some may not.
    – knol
    Commented Jan 17, 2023 at 14:35
  • @AlexTaylor I think you must be right that it was coming from the internal speaker. I knew it couldn't have been coming from the TV so I assumed it came from the cassette player. I was a small kid at the time, so my memory isn't super clear - I just remember hearing the sound whenever a game was loading.
    – N. Virgo
    Commented Jan 17, 2023 at 22:47
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Aaah, who can forget James Houston's "Big Ideas: Don't get any"? The first minute is the sound of a ZX Spectrum loading its music data. Then follows three minutes of non-musical devices attempting to produce music. Frankly, I want a flatbed scanner bass myself.

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It sounded a bit like this ;)

Breaking Baud is a Amstrad CPC / Schneider CPC tape loader demo by doz/crtc/3ln, which was presented on the Revision 2014.

It ranked 2nd in the oldschool category.

https://www.youtube.com/watch?v=D62jpqZ6TG4

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I had an MPF-II, one of the many Apple clones at an affordable price...

When I listened to the tapes, it was very similar to what a modem sounded like. More or less, it was taken from the same technology as the fax machine. Also back in the day, it was very slow. Modern modems & faxes can go way faster than those old computers could record on a tape.

The first phone system to transmit faxes was in 1964 by Xerox.

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I had both the ZX Spectrum 48K and the Amstrad CPC 464. The audio played through the tape deck of the spectrum was like someone dragging the bow of their violin on the the 1st and the 4th string aggressively both across and up and down the fingerboard. Attuned to shaving your face from side to side instead of up or down! Painful and pointless. The Amstrad had its own cassette player attached so very rarely did you hear the code being played. But you did connect it to your phone line which was as audibly painful. Like calling a fax machine number back in the day. And just to add insult to injury 70% of the 1st time load crashed and you had to endure an extra 15-30 mins of the same screeching pain. Why the Atari 3000 cartridge console idea took so long to be replicated is mind boggling.

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It doesn't sound like anything understandable by human hearing. It is basically digitalized noise, seemingly random, but still possessing a certain clean-cut quality to it that distinguishes it from a truly random white noise, and arguably makes it also much more jarring and unpleasant to listen. The closest similar thing is, imagine those digital beeps and boops, featured in movies made in nineties and before, that are supposed to telegraph a computer being busy and active. Now, imagine those beeps and boops sped up a couple dozen of times.

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Screechy and grindy, basically. Like a rotary saw grinding at metal, except somehow "smoother". Not "smooth", "smoothER". Just slightly less cacophonous. Maybe like a rotary saw cutting into a church bell.

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