The piano is king this week at the University of Maryland. (Those who may have thought the pipe organ was the King of Instruments should remember that Balzac took care of that little item by proclaiming the organ the "Pope!")

The coming week brings the College Park campus its Ninth Annual International Piano Festival and Competition. Conceived by Stewart Gordon, long the head of the Maryland piano department and soon to become head of its School of Music, piano week this year is directed by Fernando Laires.

It is the word "festival" that gives the week its special accent and atmosphere. There are other international piano competitions, some with more seniority, larger cash prizes and greater prestige. But at Maryland a lot will be going on besides the heart-in-mouth aspirations of the 30 pianists who have been admitted to the preliminaries.

Do not take any of this to mean there won't be good money for the winners of this week's contest. Eight prizes totaling $6,800 will be awarded next Saturday night when the finals are over. For that night, the 30 starters will have been na-rowed down to three. In addition to the money, 10 concert appearances will be offered to the three top winners, for which they will receive further fees. Among the special prizes are several that are especially well-conceived: a $1,000 prize to the highest-ranking semifinalist, and a $200 prize, given by the Gisriel Piano and Organ Company, for the best performance of a new work, "Ballad" by Lawrence Moss. Commissioned for this competition, this work will be played by each contestant.

Despite the special excitement of the pianistic trials, they will occupy only a small part of the week that has now begun. Every night, beginning with tonight's Bach concert by Rosalyn Tureck, there will be recitals exploring the repertoire from the Bach through Beethoven, Schubert, Chopin and Liszt; Brahms and Scriabin to Shostakovich and Stravinsky. On Thursday night the concert will be by the New Dave Brubeck Quartet, with one of the great jazz pianists of a generation in new and old specialties. This is a new touch in the Maryland piano weeks, which now draw piano students, teachers and fans from a large area.

In addition to Tureck and Brubeck, the recitalists for the week include Aleksander Slobodyanik, Jorge Bolet, Louis Kentner and the great duo-piano team of Gold and Fizdale. Each of them, except for Brubeck, will give master classes on the day following his concert. Additional classes will be given by Leon Fleisher and Eugene List, and lecture recitals by Nelita True, Alan Walker and Valerie Tryon, Thomas Schumacher, Joseph Bloch and Maurice Hinson.

A new idea for this week's festival is to offer visiting teachers special consultation sessions with members of the university piano faculty. These will be forums for the discussion of particular problems that come up in teaching technique and repertoire.

The presence on a single campus of so many masters of the piano world combined with a competition of taxing requirements, will make the Tawes Theater and the University's Adult Education Center focal points all week.

In the opening rounds of the semifinals at 3:30 p.m. this afternoon, the tension will begin to increase for the 12 who survived yesterday's preliminaries. Each afternoon through Friday, the 10-man jury will listen to and weigh the talents of each pianist. The original 30 contestants, whose average age is just over 24, have come from Jamaica, Japan, Israel, Austria, Hong Kong, England and Canada;. Within the United States, they are from states ranging from Florida to California.

They will be judged by a jury whose chairman is Eugene List, and whose members, in addition to Fleisher and Kentner, include Robin Harrison from Canada, Andre-Francois Marescotti of Switzerland, Ladislav Mokry from Czechoslovakia, Luiz Mauro-Castro of Brazil, Wiktor Weinbaum from Poland and Jascha Zayde from New York City.

Past competitions at Maryland have been juries split prizes among contestants who seemed absolute equals, refusing some prizes when no contestant was judged worthy, and fending off at least one mother who wanted to sue everyone in sight. Things are never dull during piano week at Maryland, and tickets to almost all events are available to the public. CAPTION: Illustration, no caption