NOBODY could call Ernst Kovacic a ''routinier'' and his Perth Festival concert at Scone Palace, which he shared with three expert fellow instrumentalists, was as exemplary in its planning as in its execution. The programme was like pieces of a jigsaw puzzle which, when put together, formed Messiaen's Quartet for the End of Time.

First came Mozart's Kegelstatt, or Skittle-Alley trio - a frivolous nickname for a deeply serious work - which showed how Messiaen's strange and special sound world had been to some extent anticipated in this beautiful, touching masterpiece for clarinet, piano, and viola.

Then came Webern's complete music for cello and piano, a less arduous experience than uninitiated listeners might have feared. Being hyper-taut exercises in compression, these pieces filled a tiny portion of the programme, but brought the fourth member of the ensemble into needle-sharp action before his more extended contribution to the Messiaen.

The Mozart was performed with whole-hearted sincerity and keen interplay of timbres by Kovacic (on viola) with the brilliant Pascal Moragues, a protege of barenboim and boulez, on

clarinet and David Owen Norris

as pianist.

In the Webern, presented as an inspired study in the art of ever-decreasing circles, Raphael Wallfisch made each piece spring like lightning from the printed page.

But it was the Messiaen which provided the key to the whole concert and exploited the expressive resources of each player to the utmost. In the timeless violin solo that ends the work, Kovacic sustained the violin line without limpness, though it was the Tristanesque desolation which Moragues brought to the vast clarinet solo that was surely this performance's most memorable feature.