Do they laugh when you sit down at the piano? That's probably because you have never sat down at a Bo sendorfer 290SE, a super-piano that can be yours for a mere $75,000.

"$75,000!?!?!?" you shout? Ah, but the price includes a home computer. It also includes the "blue box," an electronic/mechanical gadget that is attached to the underbelly of your piano, where it can reach into the instrument's innards and make the music happen.

Learn how to play one of these gizmos and people will show respect when you sit down to make music. Respect for the piano if not for the player.

The piano of tomorrow was demonstrated yesterday at the University of Maryland Piano Festival before an audience of about 200 merely human pianists who looked fascinated and obsolete.

The Bo sendorfer sat all alone on a stage in the university's Adult Education Center playing a Chopin nocturne, its keys pumping up and down with no human hand to guide them. The performance was not perfect, but that was no problem; it could be proofread and corrected just like the words and sentences in a word processor.

During the demonstration, an IBM PC sat in a corner of the darkened stage, glowing smugly. The IBM was playing the piano. At least, it was telling it, through the "blue box," what notes should come next, at what pace, with what subtleties of dynamics, phrasing and pedaling. The music -- not just the notes, but all measurable details of a particular performance -- was stored on a floppy disk, where the computer could read it and pass it along to the instrument.

Looked at from one point of view, the Bo sendorfer was a keyboard for inputting data -- in this case, a Chopinnocturne played by a Maryland piano student -- into a computer, just as other (differently equipped) keyboards input accounts payable, weather forecasts, editorials or urgent messages into other computers.

But a Bo sendorfer is more than just a keyboard; it is also, for some kinds of music, the ultimate playback unit. Since the beginning of recording -- that is, for about a century -- a grand piano with its complex overtones, its craggy profile of attack and decay, has been the hardest of musical sounds to reproduce precisely. No longer. To record and play back piano music with perfect fidelity, all you need is a Bo sendorfer 290SE. It is played back precisely because the "loudspeaker" is a concert grand piano.

The wired Bo sendorfer is "the ultimate recording device for piano performances," according to Morgan Cundiff, who presided at the demonstration yesterday morning. This fact made Cundiff extremely happy, because he is the curator of the University of Maryland's International Piano Archives, where they worry a lot about preserving and playing back piano performances stored on all media -- including cylinders and player-piano rolls.

The archivists have already acquired a 290SE (Cundiff showed a series of colored slides chronicling its suspense-laden trip up the stairs to its third-floor destination), and now they are looking for a way to translate their 8,000 piano rolls (some too brittle to be played) into digital data that can be read by a 290SE.

Come to think of it, a Bo sendorfer can probably distort a piano performance in playback, too, if the original were played on some other kind of piano. It could easily come out sounding better than the original -- which may be benign distortion, but is still distortion. Other things (particularly the pianists) being equal, a good Bo sendorfer produces the mellowest sound of any piano now on the market -- and the blue box in yesterday's demonstration had no audible negative effect on that mellowness.

Scene from the not-too-distant future: Floppies recorded on a Steinway are played back on a Bo sendorfer, and the purists protest -- just as they now protest Bach's harpsichord music played on a piano? Will it happen? Don't bet anything you treasure against that possibility.

If someone didn't like the way the nocturne was played, he could go over to the computer, change a tempo here, an accent there, a note somewhere else; arpeggiate a chord, or give more weight to the third finger on the left hand; add or take away a note; tighten up an attack or spread a nimbus of pedal over a whole phrase.

This will ultimately bring up a menace hitherto unimagined in musical performance: the danger of perfection.

The problem is not new, though it has never been quite so acute as the 290SE could make it. 'Way back around the beginning of the century, it is rumored, when the piano roll came along and pianists began to preserve their work for posterity, virtuosos began editing the master rolls. A bit of tape here, a touch with the scissors or paper punch there, and wrong notes would disappear, impossible octave doublings would materialize cadenzas and 32nd-note filigrees could reach levels of elaboration beyond the reach of normal human hands. Or (simplicity itself!), the tempo of the performance could be speeded up just by changing the playback tempo of the roll.

Listening to those old piano rolls and looking back, we sometimes think that there were giants on the earth in those days -- that they don't make pianists like that any more. But could some of the brilliance have been the work of an editor -- a musical cosmetician? You bet your life it could.

The facilities of a modern recording studio make such trimming and pasting look positively amateurish, and no effort is made to conceal the fact that studio recordings are routinely "improved" with retakes and splicing. It has reached the point where perfection of a sort (at least, the absence of errors) becomes the standard. And critics begin to grumble -- quite rightly -- that mere perfection is not enough.

The accepted style of performance becomes a tepid, cautious avoidance of errors rather than a reckless pursuit of wild beauty. Performers are unable to reproduce on the live stage the kind of performance they distribute on records, and they may begin to question the wisdom of setting for themselves standards that are not only impossible to attain but unworthy of pursuit.

Ads for one of the old piano roll companies used to promise purchasers "Perfection without Practice" -- a slogan that drew hearty guffaws from the pianists at the University of Maryland festival. It was never true with paper rolls. Some of them came remarkably close to the sound of a human performance, but there were subtle nuances that could not be captured in that medium.

TheBo sendorfer 290SE is remarkably -- we might say spookily -- close to the real thing. Let us say that a pianist chooses to give more power to two notes in an eight-note chord. The Bo sendorfer can reproduce that effect, and it can handle the pedals, which were always a problem for the rolls.

And with patient editing, an amateur pianist can make himself sound exactly like a Rubinstein.

Discussing the editability of digital recordings, Cundiff dismissed this aspect. It could be used for marginal trimming, correcting and polishing, he said, as the techniques of the recording studio are used, but it could not be used to transform an ordinary performance into a great performance; the work would be "too cumbersome and tedious." He may be underestimating the determination of some hard-working mediocrities.

Imagine the pianist of the future, hoodwinking the audience with an electronic performance -- the PC, which does all the playing, concealed backstage. He would be prudent to position the piano, or dim the lights, so that the audience could not see the keyboard, where an occasional key might move without being touched. And he should leave in one or two mistakes to please those (fairly numerous) members of the audience who come in hopes of hearing them.

But above all, he will pray fervently for no power failures during the concert.