Having unexplained thoughts about your dentist? Feel like you're on hold? Getting frightened of elevators?

Maybe you should stay away from 13th and L NW.

It is there, near an ordinary-looking street lamp, that passersby are immersed in a mysterious siren song. Sometimes they don't even realize it. When they do, they search the sky for a source, but it's the street lamp -- a Hifilite in front of Music Inc., the Washington headquarters of Muzak, rigged by the audio-masseurs there to add mellow melody to the sounds of jackhammers and rusty mufflers.

Music Inc. President Allen T. Smith and his engineers sometimes like to peer out their window to observe the effect their product has on the human behavior below. When the mood strikes, they can flick a switch to replace the "background" sound (101 strings-style instrumentals) with grabbier "foreground" music (soft-rock vocals). On this day, for example, a crew of construction workers is lured over almost instantly to eat lunch on Muzak's steps.

At this writing, there are no plans to wire up Hifilites along Pennsylvania or Constitution avenues. Which sounds good to us. With the problems we've got, those guys should be working through lunch anyway.