Hashtag Ensemble is a music cooperative specializing in contemporary music, improvisation, and musical education, established by flutist Ania Karpowicz in 2013. 

Hashtag Ensemble operates by creating egalitarian structures based on the multi-layered activities of its members and by building programs based on legible and usually non-musical contexts. An important element of the group's concert practice is support and presentation of artistic achievements of women – since its beginning, the group has cooperated with multiple female Composers and Artists.

Intervention operations, concerts in the backyards of Warsaw townhouses (as part of the Warszemuzik festival) or on the street (e.g. Workers Union by L. Andriessen performed with Warsaw residents at Na Rozdrożu Square) are the foundation of the Hashtag Ensemble rooting in locality and integration with local communities.

The group has been invited by European festivals and institutions, such as Warsaw Autumn, Sacrum Profanum, Intersonanzen, Sinfonia Varsovia, POLIN Music Festival, CEME Festival Israel, Tallin Afekt Festival, Poznań Music Spring, Musica Electronica Nova, Music Gardens, Warsaw Music Encounters and other.

Hashtag Ensemble performs finalists' compositions at composers' competitions: The Tadeusz Baird Young Composers Competition, Zygmunt Mycielski Composition Competition, Kazimierz Serocki International Composers' Competition.

One of the important areas of the group's activity is improvisation, which has produced three improvisational threads so far. „Visegrad Songs" (CD 2016) is a reinterpretation of motives taken from 19th-century classical music, "#WITKACY" (CD 2018) presents a musical re-reading of photographic auto-portraits by Stanisław Ignacy Witkiewicz, performed during the SOUNDLAB project in the M. Karłowicz Philharmony in Szczecin, „urb<s>core", consists of closed improvisational forms inspired by photographic scores by Zbyszek Siemaszko, revolving around the theme of Warsaw's modernist architecture. „urb<s>core" concert has been recorded for TVP Kulturawithin the Scena Klasyczna (Classic Scene). The "urb <s> core" has been developed into the "archi-solos" audiovisual project for the Sacrum Profanum 2020 festival, and the newest thread is AVE VIRUS - constant compositions based on internet scores drawn from media phenomena in the times of pandemic lockdown. AVE VIRUS CD has been released in July 2022.

Hashtag Ensemble has produced several repertoire albums: #NetworkMusic (CD 2018), which traces the group's artistic explorations and development in the years 2013-2017, „Trash Music" (CD 2018), which presents a study on the works of Wojciech Błażejczyk, "Openings of the (eye)" (CD 2020) – the world's first phonographic monograph by the composer Lucia Dlugoszewski and "First Command" (CD 2019) – an electroacoustic suite by Adam Porębski to the prose of Joseph Conrad. Hashtag Ensemble albums have been published with Bołt Records, DUX Recording Producers, and Requiem Records Opus Series.

Hashtag Ensemble is engaged in musical education, since 2016 it has been performing educational concerts of contemporary music at the Ujazdowski Castle Centre for Contemporary Art in Warsaw, within the Smykowizje project. Only in 2017, the group played 34 concerts for more than 1000 families, presenting the works of Crumb, Andriessen, Schoenberg, Penderecki, and many young Polish composers. Hashtag Ensemble also organizes workshops for composers (e.g. in cooperation with CEME festival, Israel 2020) and performers (e.g. during Afekt festival, Estonia 2018). In 2022 Hashtag Ensemble began close cooperation with Museum for Contemporary Art in Warsaw and conducts sound activities in dialogue with fine art exhibitions.

Hashtag Ensemble initiates and moderates cooperations with new music ensembles in Poland and Europe (Riot Ensemble, Meitar Ensemble, NeoQuartet, Spółdzielnia Muzyczna Contemporary Ensemble) and supports partnership building within the contemporary music environments – both musical and institutional.