For several years now, jazz-rock, or "fusion" music, has languished somewhere between being a trendy off-shoot of jazz and developing into a truly original and viable musical style. After the pioneering efforts of Miles Davis and Frank Zappa, who hinted at its possibilities, and the work of the Mahavishnu Orchestra, the prototypical fusion group, the music has wallowed in a mire of artistic pretension and commercial excess.

Recently, however, fusion has begun to mature.Many of the musicians have abandoned their "gold rush" mentality and have begun to explore the potential riches of the music. Two new releases are representative of this new approach.

French violinist-composer Jean-Luc Ponty as always a flair for cool, limpid melodies, yet in his earlier work, these served primarily as introductions for solo sections that bore little resemblance to the songs themselves. "Cosmic Messenger" (Atlantic SD 19189), also features a certain amount over-wrought instrumental riffing, yet Ponty is now learning how to make this work for - rather than against - his compositions.

"Ethereal Mood" and the title song are studies in control and restraint. Soft, arpeggiated guitar introductions give way to flowing rhythms, from which Ponty's violin emerges with melodic phrases that are harmonically transparent.

When solos are employed, they are set in a context that gives them greater definition and impact. "Egocentric Molecules," purely a vehicle for solo work, begins with a section that builds to a crescendo of pyrotechnical fireworks, and which is the perfect lead-in for the flashy displays of the guitar, violin and keyboards.

One of the drawbacks to "Cosmic Messenger" is that, while Ponty now controls the solo sections more firmly, he still relies on them when he hits a compositional snag. Many of the songs are imaginative, but they demand further thematic development. They are like musical parfaits that are delicious, but leave one hungry for more. When Ponty is able to avoid this tendency and concentrate on his stronger abilities - his melodic sense and harmonic invention - his music is at its most effective.

Weather Report began its career with an auspicious debut release ("Weather Report"), and the follow-up, the brilliant, "I Sing the Body Electric," was the most powerful experimental-jazz record of the 1970s. After that, however, the group dissolved into a funky style of music that was as commercially viable as its was artistically disastrous. The crystalline quality of their early work became brutish and predictable, as the group moved from the subtle posturings of the mind to the exaggerated postures of the dance floor.

Their new record, "Mr. Gone" (Columbia JC 35358) pursues a middle course between these two styles, with cerebal, instrumental sections that are contrasted by forceful percussion and driving rhythms.Weather Report emphasizes collective improvisation (as opposed to strictly delineated solo work), in which the musicians play off each other and the theme lines.

Keyboardist Josef Zawinul, saxophonist Wayne Shorter and bassist Jacob Pastorius have contributed compositions that are varied both in "feel" and stylistic origin. "The Pursuit of the Woman With the Feathered Hat" is a fierce, African-sounding work, with kalimbas, bells and chants that are set against droning, insect-like synthesizers. "River People" is almost disco-ish, and "Young and Fine" presents what sounds like a synthesized Big Band, while "And Then" features soulful vocals.

"Mr. Gone" and "The Elders" are the most successful cuts - the points at which the old and the new Weather Report are most fully reconciled. "The Elders," written by Shorter, evokes ancient images, with dark theme lines on the sax that are complemented by gong-like synthesizers and the quiet tappings of Pastorius' bass. "Mr. Gone" is the exact opposite - tense, fleeting images of urban life, with electronic sounds, similiar to Varese, creating a steel forest chirps and clanks that evolves into a cool jazz melody that echoes their earier work.

"Mr. Gone" is a remarkable record because, rather than being a renunciation of commercial values, it is an attempt to combine profundity with performing music that is as enjoyable for the listeners as it is for the accountants.