Aggregation No. 1Tenth annual Honk! Festival of Activist Street Bands all weekend in Davis Square. Free.

This signature Somerville event starts Friday with Lantern Parades from 7:30 to 8:30 p.m. (earlier in the day there’s a lantern-making workshop) followed by a performance at Johnny D’s, 17 Holland St., Davis Square, as well as action at the “Visaural: Sight, Sound and Action” art exhibit with a “Honk! Around The World” component at the nearby Nave Gallery Annex, 53 Chester St. starting at 6 p.m. The main thing, of course, is a Saturday full of performances by 28 sociopolitical activist street bands from as close as Somerville and as far away as Paris; Los Alamos, N.M.; New Orleans; and Montreal and Quebec City. On Sunday, a noon to 2 p.m. Honk! Parade brings street bands from Davis Square to Harvard Square (a parade route is here) so the activist marching bands can take part in Cambridge’s 37th annual Oktoberfest. Information on the weekend is here.

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Aggregation No. 2Loop 2.4.3’s “Time-Machine_music” record release show at 8 p.m. Friday at Lilypad, 1353 Cambridge St., Inman Square. Admission is $10 at the door.

New York City composer Thomas Kozumplik (also know as Loop 2.4.3) brings music from his fourth album to Cambridge with New England pianist and electronic musician Istvan B’Racz. Gramophone calls the work “Visceral and satisfying … an astonishing variety of brand-new yet iconic sounds that create a riveting aura, a genuine time warp,” but basically it’s just mesmerizing music that has to be heard to be fully appreciated. Luckily, The New York Times says Loop 2.4.3 gives “intricate, energetic performances.”  Information is here.

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Aggregation No. 3Space Park Pop-Up Solar System Playground from noon to 8 p.m. Saturday at Perry Park, 355 Washington St., Somerville. Free.

Made possible through the collaboration of artists, science teachers, students and engineers, this scaled re-creation of the solar system by artists is called by organizers “the holy grail for supporters of science, technology, engineering, arts and math.” From noon to 5 p.m. comes the more educational component of the day, including a gigantic interactive labyrinth representing the International Space Station and a reading area provided by The Somerville Library; from 6 to 8 p.m., music is added to the mix. Information is here.

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Aggregation No. 4Harvard Square’s 37th Annual Oktoberfest from noon to 6 p.m. Sunday in Harvard Square. Free.

Attended annually by more than 200,000 people, Harvard Square’s Oktoberfest features food from all over the world, arts, crafts, vintage goods, sidewalk sales and one-of-a-kind gifts. There’s music, dancing and children’s activities, as well as beer gardens hosted by Alden & Harlow, Charlie’s Kitchen, Fire + Ice, Grafton Street and Night Market. (And Beat Hôtel, 13 Brattle St., transforms into a Bavarian Beer Hall with community tables, German food, a live oompah band, lederhosen, dirndls and an assortment of German beers.) A noon to 1 p.m. Honk! Parade brings the Davis Square street festival to Harvard Square – a parade route is here – so the activist marching bands can join other music performances on six stages all around Harvard Square. Information is here.

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Aggregation No. 5Fourth Annual Festival of Dumplings from 1 to 3 p.m. Sunday in Central Square.

In honor of the late chef, restaurateur and entrepreneur Joyce Chen, there are $1 dumplings for sale at seven restaurants throughout the square – Patty Chen’s Dumpling Room; The Middle East and Zuzu’s; Thelonious Monkfish; India Pavilion; Naco Taco; and Dosa Factory – and a chance to win a gift certificate package by buying dumplings at them. Information is here.