A very attractive triad, probably for sophisticated readers rather than spaceopera buffs. In Richard Frede's charming, funny ""O Lovelee Appearance of The Lass from The North Countree,"" a hack artist hired to paint a cloudscape finds himself suddenly trapped in a not-so-innocent childhood daydream of his patron. C. L. Grant's low-keyed ""A Glow of Candles, A Unicorn's Eye"" quietly portrays two actors' rebellion against the drama of the future, dominated by meaningless improvisation and a basic contempt for words. Malzberg himself contributes ""Choral,"" a dazzling story of a man hired to impersonate Beethoven by a time-traveling cult which maintains that the fabric of the past will collapse if not continually relived by surrogates from the present. (This last, with its intricate speculations about causality and freedom, is by far the most demanding of the three.) Excellent, for those who are up to it.