A sound collage featuring four seconds of music from 60 composers, assembled into a “Chained Melody.” A pianist who will let you choose notes and song titles and then improvise a piece on the spot. More than 30 live events around the country, tweeting into a giant tweet deck in downtown St. Paul.

These activities and more are part of the first National Composer Night Out on Thursday to celebrate the 40th anniversary of the St. Paul-based American Composers Forum (ACF).

And who knew that composers ever go out?

“We’re supposed to stay inside,” joked Minneapolis composer Libby Larsen, co-founder of the ACF.

Actually, the goals Larsen and fellow graduate student/composer Stephen Paulus set when they got together in 1973 were to figure out how composers could get their music performed outside of academic settings and how they could make a living beyond teaching.

They came up with the idea of the Minnesota Composers Forum, which evolved into the ACF two decades later. The organization now has more than 2,000 members in 50 states, and its record label, Innova, has released more than 450 titles. ACF is involved in recording, funding, educating — about 20 percent of the members are students — and outreach, including a daily radio program heard on 152 public stations.

“We started out wondering how we could be professionals,” Larsen reflected, “and it really has become a guild for composers.”

Michael Anthony, a former Star Tribune critic who has written about the forum since its inception, said a key turnaround was when Linda Hoeschler took over as executive director in 1990.

He explained, “She said the focus needed to shift from putting on new-music concerts at the Walker [Art Center], attended by the same 30 or 40 people — the beards and sandals crowd — to becoming a genuine service organization aimed at advising its growing membership on skills that music schools never teach: how to write grants and how to get commissions. ‘Is there a small town that wants a choral piece for its centennial? We have the composer for you.’ ”

ACF connects composers with money and commissions through McKnight Fellowships and other vehicles.

25 albums annually

Innova releases about 25 albums annually from many genres — from new classical and jazz to electronic and world music. CDs are distributed via Naxos, and the music is available on iTunes, Amazon and other online outlets.

“One hundred percent of sales go to the composer and musicians,” boasted ACF President John Nuechterlein.

ACF serves composers, not songwriters. What’s the difference?

“We are of the same genus, but we’re slightly different species,” Larsen said.

Songwriters are more like jewel setters, she said: “The song is the object. The form shifts a little bit, but it’s dependent on the words and the memory of the words.”

Composers, by contrast, are like architects. “A composer like myself, I think about the architecture of the sound, and how a person remembers music in many different ways.”

St. Paul bash

Nuechterlein has been planning the 40th anniversary celebration for more than a year.

The big bash will be at Landmark Center in downtown St. Paul, emceed by Bill McGlaughlin, former Minnesota Public Radio host and St. Paul Chamber Orchestra conductor. The event will feature the world premiere of “Chained Melody,” a tapestry of four-second compositions — one second for each decade — from 60 composers sent to ACF. A 10-minute video about ACF will have its premiere, as well.

There will be live performances by Orange Mighty Trio, Jelloslave and Minnesota Boychoir, which will offer a new ACF-commissioned piece. The VocalEssence Ensemble Singers will perform the world premiere of Kim Andre Arnesen’s “Child of Song.” Compositions by Larsen and Paulus, who died last year, also will be performed.

And a giant tweet deck and video projections will enable folks in Landmark Center to monitor other National Composer Night Out activities. In Boston, there will be a discussion about black composers. In Oakland, Calif., there will be an open mic for improvising using only three pitches — A, C and F. In Montana, a pianist will let you pick five notes and two song titles and he’ll weave them together into a piece. And, in Birmingham, Ala., there will be a listening party and scotch tasting.

Can’t wait to see how well-composed the tweets are from that gathering.