IF RALPH GOCHNOUR looks familiar, it may be for one of two reasons. First, as longtime second flute of the Utah Symphony (since 1956) he has commanded a certain visibility at its concerts. Or you may recognize him from his appearances - some of them on national television - with his other great pastime, his model trains.

Gochnour admits there are larger collections in town. "Some people walk up and say, `I've got 179 brass locomotives,' but I've never been interested in keeping score. I probably have around 200 and there are certainly people that have quite a bit more. But I also have a finished layout - again, I won't say others don't - but most people with big collections don't or, if they have a layout, they don't have a big collection."If his seems to have received a disproportionate amount of attention, it may also have something to do with his willingness to let it be displayed. Gochnour speculates that there may be anywhere from 15 to 20 larger and more elaborate layouts in the Salt Lake area, including one right up the street. "But a lot of these guys don't want publicity," he says. "They're afraid that if their stuff is seen it's going to be ripped off."

Gochnour isn't afraid of letting his stuff be seen. On the contrary, as one descends the basement stairs he is greeted by a sign with an arrow that, just like the ones in the depots, says, "To trains." The arrow leads to a combination family and hobby room, its walls adorned with photographs and display cases housing an impressive array of locomotives, diesel and steam, most of them patterned after Union Pacific prototypes.

Sizes run from an early standard-gauge Lionel - one of the few "toy" train, or tinplate, models on view - to the HO scale (and smaller) that dominates Gochnour's layout.

The layout itself is remarkably compact, given everything it contains, occupying 13 by 21 feet along the north wall. It is Gochnour's fourth and has been 18 years in the building. "The first was a small 3-by-4 layout I started when I was in college," he recalls. "It was so small I could throw it in the car, and in fact it ended up as part of my first major layout just after we got into our first house around 1960."

His present home, Gochnour confesses, was selected with an eye toward its railroading possibilities. "Which meant that other than accommodating a growing family it had to have enough empty space in the basement to accommodate my dream layout."

The terrain will look familiar to Mountain Westerners, a recollection not only of parts of northern Utah but Gochnour's boyhood home in Burley, Idaho. Called the "Bear Gulch and South Western" line, the track, overlaying miles of hand-laid ties, runs from Wahsatch Junction (the room proper), with its extensive scale-model roundhouse and switching network, to the little mining town of Bear Gulch, northeast of the central control complex.

From the carefully weathered boxcars to the electric trolley that glides past the junction at regular intervals, one notices that not only is everything in scale (the tiniest train being at the very rear, to lend a sense of perspective) - it is also in period. As the trains themselves are all based on real-life prototypes from the late '30s through the early '50s, so are the miniature trucks and sedans that dot the roadway (complete with blinking red-and-green traffic lights).

Ditto the landscape. Gochnour points with pride to a bridge patterned after one in Twin Falls and another based on a Kamas Prairie R.R. trestle he photographed from the bus window while on tour with the symphony. Above that sits a working oil derrick, whose prototype he spotted in Evanston, Wyo. A coaling trestle not too far away had for its original a similar operation in Provo.

"Basically you're modeling what you've experienced," Gochnour says, "plus a lot of imagination."

That imagination has led him to come up with some novel twists and go a bit farther in the "animation" department than some of his colleagues. Since I was last involved in the hobby, sound effects appear to have come in with a vengeance, and via a complicated control panel of its own Gochnour can pipe various sounds into his engines, each equipped with its own receiver. (My favorite: the faint "lurching" noise the metal, steam and rubber make as the train pulls slowly out of the depot.)

Each he defends not as a toy but as part of the quest for enchanced realism. For example, around 10 years ago he supervised the development of a light that to the naked eye appears smaller than a pinhead; it now can be seen blinking, in various colors, from cabooses and even switch signals - the first time I have seen anything quite that detailed.

A self-propelled pile driver sitting nearby is not only meticulous in its detail; it actually works, coming to attention via remote control and hammering its post into the ground (or whatever) via electronic timer. This, Gochnour assures me, was not part of the original kit.

Nor was the pipe-laying operation one sees taking place under some of the track over by the junction. Gochnour relates how in the winter the board joint had a tendency to split at this point, so he simply made a virtue of necessity and transformed it into a pipe trench. (The small plastic pipes themselves had to be imported from England.)

Various other details catch the eye: a flickering flame in the fire of a hobo jungle below Bear Gulch, a Gold Seal Guernsey dairy car loading a "Gochnour Brothers Dairy" truck ("so I could get my dad in the picture"). But the "pride of the fleet," as Gochnour calls it, is a remarkably accurate replica - including besides the engine all 11 cars - of the U.P.'s City of Los Angeles passenger train, circa 1941.

So vast is the layout's network of tunnels that at first I don't even see it. It is only when Gochnour slips behind the curtain that leads underneath to the control complex (a deliberately theatrical touch?) and revs her up that she finally emerges, long, yellow and sleek. And so lengthy are some of those tunnels that at one point the train disappears for several minutes, only to re-emerge west of Bear Gulch heading the other direction!

Obviously this is a love that has had to balance itself against Gochnour's flute-playing. As it happens, he got his first flute two years before he got his first train, at age 12. "Then, when I was 14 and my younger brother and I got the proverbial Lionel, I wanted to be a railroad engineer. But a couple of years later I decided I didn't want to do anything but play the flute and that won out, but the other tagged along in miniature."

It has also had to balance itself against family, but here Gochnour says he is luckier than most. "Obviously I've done a lot of chasing trains through my life, and I've always tried to include Rosie," he says of his wife. Apparently it worked because upstairs, ringing the Christmas tree, is a German train set she brought back from the symphony's last European tour.

"Too many wives consider the hobby a rival," Gochnour observes, "for time, attention, money. But if a wife is smart she will try to share that interest. As a result we've had so many wonderful train trips together and friends we enjoy all over the country. And at least they know where we are.

"For example the last time we were in L.A. on tour, and most people were out on the town, I was in the train room of my good friend Jeff Reynolds, who is bass trombonist of the L.A. Philharmonic, having a delightful evening. Conversely when the L.A. Philharmonic was here a few seasons ago, after the concert Jeff was in my basement."

Undoubtedly taking a ride, complete with lights and whistles, on the Bear Gulch and South Western - shall we say con brio?