THE MOST FASCINATING recording I heard last year arrived in that year's final weeks, struggling under the burden of a lengthy title, but one that told with fine precision what the record was all about: The Roots of American Music: Renaissance Melodies in Traditional Music of the New World (Advent Cassette E 1062, $8.95). Performed by the Boston Camerata under the direction of Joel Cohen, the cassette was recorded during a performance at Harvard University's Sanders Theatre - like Washington's Folger Theatre, a perfect setting for early music. What it amounts to is a musical dialogue across the centuries and the continents - a study of some of the tunes that were brought to this hemisphere by settlers from Europe, and of what happened to them here. It is, inevitably, a "learned" sort of program, deeply steeped in Renaissance and Medieval musicology and in the very different scholarship related to folk music on this continent, but it bears its learning with a very jaunty air, and moments of pure, heart-stopping beauty abound in it.

I am particularly glad that it arrived on a cassette rather than a disc for several reasons. It lasts just over an hour and 14 minutes, a length awkward to put on discs but perfectly simple in the more flexible tape medium, and I can't find ten seconds in the whole program that I would want to see edited out. In addition, tape is able to take the kind of repeated playing I have inflicted on it (particularly a few favorite passages that I find beautiful beyond description), while a disc would have had some of its grooves worn flat by such treatment.

The program announces its basic intention from the very beginning, opening with a May Day dance from 12th-century Provence and continuing with a close cousin of the tune transcribed from contemporary New Mexico. It also surveys the polyphonic church music of Renaissance Spain that was brought over intact to Mexico and Peru more than four centuries ago, the tunes that migrated from France to Quebec and (a particularly fascinating subject, though less exotic) the transformation of English into American folksongs.

Besides the dialogue across time and space, the music contains a dialogue between folk and classical music. At one point in his spoken commentary, director Cohen refers to the "perfectly awful" setting of an old tune by Respighi in his Ancient Airs and Dances. I bristled at that phrase, for I have loved that tune 20 years or more, specifically in Respighi's setting, and I have always felt specially grateful to that sometimes rather tasteless scholar-composer for rescuing this melody from the dusty oblivion of the archives. This tune is performed by the Camerata about five minutes before the end of side 1 - around number 480 of the turn-counter if you are using a cassette deck with the counter attached to the left-hand reel. And listening to it, I must concede Cohen's right to look down on Respighi. The old Burgundian dance tune is seamlessly blended into a Quebec folksong, its performance is one of the most perfect presentations of old music I have ever heard, and if you play it with Respighi's modern orchestral treatment running through your mind in a sort of counterpoint, you begin to understand why the old instruments are the best vehicle for old music.

There are many other absorbing moments - five variations on the "Barbara Allen" tune in three languages, for example; an enchanting look at the "Gipsy Davy" and an Elizabethan relative; a brief, fascinating survey of the folk polyphonic tradition in religious music that began in the English colonies and continues today in the South. This cassette has a remarkable quantity and variety of music for a brief concert, very thoughtfully selected and arranged, and beautifully performed.

Briefly noted below are some other interesting recordings devoted to Americana:

A Nonesuch Treasury of Americana. Various artists (Nonesuch H7-14, two records). For approximately ten years, rather haphazardly at first and more systematically of late, Nonesuch (a subsidiary of Elektra) has been digging into the rich lode of American music and coming up with pure gold. This is a sampler drawn from more than two dozen records which have given fresh life to the music of wellknown and unknown composers, classical, popular, ragtime and unclassifiable; colonial, Victorian and modern. There is no series of recordings this side of the Deutsche Grammophon Archiv that has given me more combined pleasure and enlightenment, and I recommend this sampler heartily. Compared to a complete set of the originals, it is second-best, but it is still very good.

Ives: Piano Sonata No 2 ("Concord, Mass., 1840-60"). Gilbert Kalish, piano (Nonesuch H-71337). Ives: Complete Works for Solo Piano. Nina Deutsch, pianist (Vox SVBX 5482, three records). The Kalish Ives performance is a fine sample of what has made the Nonesuch Americana series so great. It is a deeply thought-out, technically superb, brilliantly recorded presentation of one of the basic landmarks in American music, and no serious collection should be without it. Deutsch's survey is more problematic but nonetheless commendable; it is not quite "complete," as the title claims, though it contains a good bit of unfamiliar material, notably a startling march Ives wrote while he was still a student at Yale, some sketches and elaborations based on the "Emerson" section of the Concord Sonata and Deutsch's transcription for piano of the brilliant America Variations, as well as other short pieces and the two big sonatas. In the better-known pieces, this recording runs into some high-powered competition, with which it competes honorably if not always triumphantly. Throughout the performance and the essay packaged with it, we are clearly in touch with an artist of solid technical skills, one who has immersed herself thoroughly in the mind and idioms of Ives and who frequently offers fresh insights, worthy alternative approaches to music which (more than any other, I think) must not be allowed to petrify into a single "standard" interpretation.