If "metal tape" has you puzzled, you are not alone. Disagreements over its technical aspects as well as its potential effect on the market are rife within the industry.

Its correct full name is "metal-particle tape." It is a plastic ribbon that looks like regular tape. What's different is that the magnetic coating is made not of oxide but of "pure metal" particles. Compared with oxide tapes, the metal variety is less prone to signal saturation. That means it can offer improved response, lower noise and less distortion.

As with any tape, these performance aspects can be traded off among each other when used on a given tape recorder. For instance, it is possible to adjust recording bias to extend the high-frequency response, but if this is pushed too far the distortion rises. In any event, even with the trade-offs, the potential for improved performance in all areas is greater with metal tape. t

To realize this potential, however, metal tape requires higher bias currents than those used for oxide tapes. It also is harder to erase, and thus needs stronger erase currents, too. These higher currents, in turn, create the need for new tape heads that can handle the increase.

Although metal tape is available so far in very limited quantities, several equipment manufacturers have announced new cassette decks that will handle it. This may be a bit of jumping the gun, since metal tape is not (at least in the foreseeable future) regarded as a mass-market item. And no one in the industry wants to imply that suddenly all existing tape recorders are "obsolete" simply because they cannot fully handle metal tape.

Actually, while some companies may be promoting the cart before the horse, the new metal-tape-capable recorders also handle the existing varieties of oxide-coated tape. So nothing is lost if you happen to be in the market for a new cassette deck and decide to buy one with metal-tape capability.

What about using metal tape on one of the many million units now in use that lack metal-tape capability? On such a machine, recording with metal tape will get you somewhat brighter highs. It also will -- depending on the recorder's own characteristics -- produce some higher distortion, especially at very strong signal levels. If you try to re-record with that same tape, you very likely will find that the previous material has not been fully erased. In my own experiments along these lines, I found that the previous program could be heard faintly during soft passages of the music I recorded a second time.

If you play a prerecorded metal tape on a non-metal tape deck, the highs will also sound brighter, But there probably will be no increase in distortion on the playback.

Metal tape will not damage a recorder or increase its head wera. Thus, the aficionado who buys a metal-tape deck and records a metal-tape cassette on it can play that cassette on any other machine -- including the one he may have installed in his car -- without worrying about harming the latter unit.

Prices for metal tape seem to be lower than expected. Early estimates were that it would cost two to three times more than oxide tapes. For instance, 3M's new Metafine 46 (23 minutes per side) sells for $6.25. 3M's premium oxide tape, Master III, costs $4.19 in the C-45 size (22.5 minutes per side).