Regarding the comments a page or two back about the difference in longevity between reel-to-reel and cassette tapes, I remembered that my best friend -- and major audio technician with his own recording studio -- Rocco Fortunato has major knowledge of these technologies from our past. I asked him if he would be willing to fill us in a little bit. Well....... you will quickly see that we are indeed like brothers. Here is his "little bit." All very informative:
I do note that someone mentioned Reel tape being more robust than cassettes - yes and no. Cassettes are made from the same kind of magnetic tape stock as 1/4" Reels - albeit cut much narrower (1/8"). So, yes, cassettes are mechanically less durable. They stretch more easily in cheap players and can tangle in slot-fed players pretty easily. You wouldn't sound good either if you were stretched and wrinkled... wait a minute... that's what's happening to ME in my old age.. oh, never mind...
But the tape itself can last as long as 1/4" reels if handled properly. And believe me, 1/4" tape can be stretched and wrinkled too. And it can be scratched by worn tape heads. And: If a tape is played on an old machine (actually any machine) that has not been maintained carefully, the machine will degrade the magnetic signal on the tape, progressively eroding especially the high frequencies permanently with each play.
It's a kind of mutually destructive ballet between the tape and the player. The tape has a coating of iron oxide, each particle of which is a tiny permanent magnet. A build up of magnetic flux is transferred to the tape head block by the iron oxide on the tape itself as it passes by the head. Think of magnetizing a screwdriver by passing a permanent magnet over it. The tape is magnetizing the tape head!
When the tape head's job is recording, it generates variances in magnetic flux to force the iron oxide particles on the tape surface into magnetic patterns that represent the sound. The recording head is a controlled magnet. The playback head is not supposed to be a magnet at all. It's job is to read all the little magnets on the tape. If the head has any magnetic properties, it changes (re-records, if you will) the sound of the tape!
In the days when I professionally recorded to tape, it was essential that the tape machine heads be fastidiously cleaned and demagnetized constantly: every day and before every critical recording or transcription. How long has it been since the tape heads in a typical car cassette player were cleaned? You can't even get a demagnetizer in to the heads without dismantling the dashboard. Car players are notorious for destroying cassette tapes. Now you know that not only can they chew them up and spit them out as spaghetti, they insidiously magnetically degrade your good tapes with every play. It's probably why cassette tapes have a poorer reputation than 1/4" reels for longevity.
Of course, tape materials and qualities also vary. Recording tape is a long strip of material with iron oxide glued onto it. The formulation of the iron oxide compound is critical and varies by brand and expense level. So does the quality of the strip material and the glue. I have tapes from the 50's that still play ok and tapes from the 70's that are crap. And vice-versa! Some old tapes have glue that has dried up to the point where the oxide falls off in clumps as it passes by the head. Or worse, some glues turn gummy and clog up the head with goo.
The backing strip longevity varies by both original material choice and quality of manufacture. Some materials , like acetate - used in most very early tapes - dries out with age and breaks very easily. I once had to do a project of transcribing a series of old tapes that had PAPER backing. I was cleaning heads and rollers every 15 minutes and became more experienced with a splicing block than I had ever imagined! More durable materials, like mylar - invented later - suffer from stretch problems that cause the oxide to flex off the tape - or simply change the s-ooo-uuu-nnn-d.
Commercial tapes, like the Alamo prize mentioned, suffered from the need for the manufacturer to squeeze longer program material onto each reel. Standard tape would only get you 20 to 30 minutes of play on a reel. To get a standard reel to play for an hour and maintain fidelity, the solution was to use thinner tape! Stretch city! And, for a machine with a dirty pinch wheel, spaghetti waiting for sauce.
Bottom line: tape is a durable medium with longevity only if it's materials are of lasting quality, it has been stored where air and moisture haven't messed with the glue or the backing, and, most importantly, it is not played on a machine that wants to eat it! (Not just mechanically -- magnetically as well.)
A word about CDs and longevity. Except for breakage, stretching, warping, scratching or oxide falling off the backing, when tapes and vinyl wear, the sound degrades gradually. Typically, it loses it's higher frequencies and overall volume deteriorating further and further into the backgound noise that was always there but never noticed as much.
With CDs, it's pretty much a yay or nay situation. If an encoded digital 0 or 1 wears on a CD, the laser can't read it at all! Nothing. If the wear isn't too bad yet,
Now the kicker. There are two fundamentally different kinds of CDs: computer recordable CDs and physically manufactured CDs made from a glass master.
The CD somebody copied for you or one you made on your computer is dye based system. A thin layer of light sensitive dye is sandwiched between two layers of plastic (or sometimes between plastic and lacquer or other materials). Also in the sandwich is a reflective layer under the dye. The recording laser 'burns' holes in the dye for digital 1's and leaves the dye opaque for digital 0's. 'Burn' means that the intense light from the laser causes the dye to turn transparent. When the playback laser reads the disc, if there's a hole, the laser light bounces back off the reflective layer underneath. Digital 1. If there is no hole, no light reflects back. Digital 0. The problem: the dye is light sensitive and also degrades chemically over time. Put that disc on the dashboard of your car and, over time, sunlight will start turning all the dye transparent. Keep that disc too long, even protected from light, and the dye turns transparent on its own. Hey, and how bout that laser light in the CD reader! Not much damage per play, but over time... Bummer. Bad disc!
HOWEVER, physically manufactured, glass master discs are completely different. The 1's and 0's are represented by stamping physical indentations in a reflective foil. No dye. When a laser hits a flat surface, it is read as the light bounces back. When the laser hits a 'dent', the light bounces away at an angle and is not read. The key here is: nothing to deteriorate. Metal foil lasts a very long time, especially when protected from the elements by a rigid, sealed plastic sandwich. Given quality manufacture, glass master discs are estimated to last a hundred years or more... but of course we don't have proof yet...
Most commercial discs by recording labels are physically manufactured. It is fair to say, since the playback process does zero harm - no wear at all - most of these will last far longer than a typical LP or tape; albeit the disc is not physically damaged by scratches or dirt. But those are user-caused wear that can be avoided. Unlike the tape player or turntable that is constantly conspiring to wear down its victim with a thousand tiny cuts, the CD player, even a cheap one, doesn't even touch the CD!
(from Rocco Fortunato, Cavalry Productions, Brackettville, Texas)