When Laura Nyro sings: "My innocence, my innocence comes from my warm earth mother," her confiding voice trembles slightly as it rises above the soft-rock beat and falls slightly behind it. The vulnerable innocence of the vocal invites a protective closeness.

But her band soon stiffens the backbeat and Nyro joins the momentum to assert that "My innocence is a wild thing." To prove her point, she unleashes her guitarists on a blustery, metallic break. Her natural innocence is no longer energy to make the most of Far more than the lyrics. Nyro's music depicts the transition from vulnerability to assertiveness.

This, of course, is a transition that many women have made in recent years. Yet because there are still so few accomplished female songwriters (as opposed to interpretive singers) there hasn't been much music to reflect this change. It's not too difficult to write lyrics about consciousness-raising, but it's an achievement to compose and arrange music that evokes the tension between old/receptive and new/aggressive emotions.

Laura Nyro's "Nested" (Columbia JC 35449) achieves this brilliantly and Wendy Waldman's "Strang Company" (Warner Brothers BSK 3178) only slightly less so. Songwriter Chris Williamson, a D.C. favorite, once remarked that young female songwriters had two prime models - Joni Mitchell and Laura Nyro. For most of this decade, however, Nyro has been an absentee model.

She released "Christmas and the Beads of Sweat" in 1970, nothing in '71, a collection of oldies in '72, nothing in '73-'75, a disappointing comeback album in '76 and a live album of old material last year. "Nested" is her first collection of strong, new material in eight years.

The songs reflect a desire to be open about weaknesses while reaching out for a confident initiative. Nyro holds onto the vocal reveries that rise unexpectedly in mid-line as if the singer had drifted off into a secret thought. She also holds onto her irregular lyrical lines: the pauses and rushes indicate the difficulty and yet eagerness of revelation.

She reaches out for musical elements only rarely employed by female pop composers: pointed rock 'n' roll guitar, multiple percussion, off-harmonies, jazz textures. On "Springblown," she sets up a simple but catchy rhythm on acoustic guitar that betrays both her folk and doowop roots. Yet, by the end of the song, her accents are followed by reverberating bass, slide guitar, and rippling congas. The result is an enchanting, accessible love song with a background off-rhythms, counterpoints and darker emotions.

Two songs in particular combine the condensed eloquence of Nyro's best lyrics with ambitious composition. They deal with the painful adjustments both men and women must make when sexual roles change. "American Dreamer" details the disorientation of an innocent suddenly face-to-face with the power struggles of business and marriage contracts ("oh big deals/cops and robbers/oh America"). But she resteadies herself and exits with a confident vocal over charging music.

On "Mr. Blue (The Song of Communications)" she reaches out to men who feel threatened by newly-as-sertive women, men who say: "I mean I've heard of liberation/but sweet-heart/you're in outer space."

The richness of the music evokes both the difficulty and the effort to overcome these new barriers. The melody aches with a longing that is only satisfied by the multi-level, double-tracked vocal harmonies at the end.

Wendy Waldman is one of those young songwriters who saw Nyro as a model. Despite a lack of recognition, she has made four of the best recent records by a female songwriter (particularly the brilliant 1975 "Wendy Waldman"). On her new album, she too combines vulnerability and assertiveness.

"Strange Company" makes several departures for Waldman. Rather than using interchangeable L.A. session musicians, she has assembled her own band and worked with them for a year. She moved still further from Hollywood's musical closet by recording in Seattle with Heart's producer, Michael Flicker.

Flicker has obviously encouraged her to use more aggressive percussion and more metallic lead guitars. The benefits are obvious on "Train Runnin," where Waldman rides the gathering momentum of the rattling piano and buzzing guitar to initimidate all obstacles out of her way. Waldman's mournful lament on "Since Love is Gone" pauses and then seems to unleash the harsher emotions of a blues guitar solo.

But unlike Heart's Ann Wilson, Waldman has not given up vulnerable revelation in acquiring a hard-edged challenge. Like Nyro and Fleetwood Mac's Christine McVie, she is able to work a musical mixture of both receptiveness and argument. As in McVie's Beach Boys-influenced arrangements, Waldman uses each instruments as an independent variable - rather than as mere accompaniment.

These independent elements make possible the stunning mixed emotions of "The Wind in New York City." The song opens with a surprisingly effective slow, blues synthesizer followed by an ethereal vocal reverie. The actual song begins with a painful depiction of nights alone after being deserted. But the counterpointed themes of the song gradually gel into a musical resolution that backs up her resolve to carry on without longing or bitterness.

For several years, male composers like Bob Dylan, Jackson Browne, Neil Young and Brian Wilson have been struggling to open up a vulnerability in their songs without sacrificing the directness of rock 'n' roll. Nyro, Wadlman, McVie, Karla Bonoff and the McGarrigle sisters are coming from the other side - trying to take hold of harsh aggressive emotions without letting go of softer, more delicate feelings.

As the two sides approach each other, they are creating a new music that is more complete, more balanced and much healthier than any of its predecessors.