After finishing the cataloging on Mats Gustafsson's latest in his Hidros series, Hidros 9, I took the time out to make sense of the series, which started in 1997 when Gustafsson formed his Nu Ensemble, or more properly, Nu-Ensemblen, with a work for nine improvisers, tape and conductor. Commissioned by The Swedish Broadcasting Corporation P2, this started in motion a set of morphing concepts and ensemble structures to interpret Gustafsson's evolving concepts. It's not clear if the title of the series derives from the Greek mythological create Hydra,a mythical serpent with many heads, but it's an apt description of the diversity expressed in each performance.

Each Hidros is developed with a specific configuration of performers, and Gustafsson has access to some of the finest improvisers and contemporary performers. Check the participants of the first Hidros as a prime example:

Axel Dörner - trumpet
Gunter Christmann - cello, trombone
Per-Ake Holmlander - tuba, cimbasso, aluminium tube
Mats Gustafsson - soprano, tenor and baritone saxophones, fluteophone, French flageolet, conducting
Fredrik Ljungkvist - tenor and baritone saxophones, clarinet
Fred Longberg-Holm - cello
Sten Sandell - piano, prepared piano, pipe organ
Barry Guy - bass
Raymond Strid - drums

At the time the comparison was made to the London Jazz Composers Orchestra, and it's an easy stretch to see Gustafsson expanding the working band Gush with Sten Sandell and Raymond Strid into a similar organization, particularly finding Barry Guy among the ensemble players.

Hidros 2 is the least documented of the series, first presented in 1999 and presented as a graphic score at his 2019 for a performance at Trondheim of a new work titled Hidros o.T.; I personally would be fascinated to hear a recording of Hidro 2, but to my knowledge there are no recordings of that work.

In contrast, Hidros 3, dedicated to Patti Smith, is well documented, recorded live October 9th, 2000 at Ystads Konstmuseum during Kulturbro 2000 and performed with Sonic Youth in a 9-part work for voice, processed voice, and contrabass sax. The guitar-heavy version is unique to the series, and Kim Gordon's voice adds an unusual character to the concept.

Hidros 4 happens the next year, performed live at Culturen, Västeräs, Schweden, May 10, 2001 with another exceptional electroacoustic version of the ensemble. Returning are Axel Dörner and Per-Ake Holmlander, the complement brining stellar improvisers including Carlos Zingaro, Thomas Lehn, Paul Lovens, Daunik Lazro and Wilber de Joode. This album is available as a digital-only release on Trost, and is well worth adding to the collection; I hope one day it, as with Hidros 2, will be released on CD, or in a box set collecting all the Hidros series.

Mats Gustafsson - saxophone
Axel Dörner - trumpet
Sebi Tremontana - trombone
Per-Ake Holmlander - tuba
Daunik Lazro - saxophon
David Stackenäs - guitar
Thomas Lehn - live electronics
Carlos Zingaro - violin
Wilber de Joode - bass
Paul Lovens - drums

Hidros 5 is a bit of a mystery, performed in 2004 in a concert at Blæst, Gustafsson with the Trondheim Improvisation Ensemble in a performance of three works by Gustafsson: "PLUGS" (2000), "Hidros 5" (2003) and "Bird Notes" (2002/03). Again there appears to be no recording of this entry in the series, or explanation for why Nu Ensemble is replaced with the Trondheim Improvisation Ensemble, which was a then-new ensemble that may have been represented by as many as 30 musicians.

Hidros 6 takes the subtitle Knockin' in another large ensemble of 13 players, including Joe McPhee, Paal Nilssen-Love, Peter Evans and Dieb13. This version was recorded i2013 at Manggha, Krakow, and exists on CD, as 2 LPs and in a complete 5-CD version.

Ingebrigt Håker Flaten-Bass
Jon Rune Strøm-Bass
Christer Bothén-Bass Clarinet, Guimbri
Paal Nilssen-Love-Drums
Mats Gustafsson (tracks: A to D)
Agustí Fernández-Piano, Organ
Mats Gustafsson-Saxophone [Slide Sax], Tenor Saxophone [Tenor Sax], Bass Saxophone [Bass Sax], Electronics, Piano [Piano Mate], Conductor [Conduction], Composer
Joe McPhee-Trumpet [Pocket Trumpet], Tenor Saxophone [Tenor Sax], Organ [Space Organ]
Peter Evans-Trumpet [Trumpets]
Per-Åke Holmlander-Tuba
Dieb13-Turntables
Kjell Nordeson-Vibraphone [Vibes], Drums, Idiophone [Flexatone], Glockenspiel
Stine Janvin Motland-Vocals

Hidros 7, subtitled Zap and dedicated to Frank Zappa, completed a set of performances In Stockholm, Poznan, Krakow, Warsaw And Wels Unlimited in 2016, first premiered in Sardinia. There doesn't seem to be a recorded version, but there is a YouTube video of the Wels Unlimited version in Austria:

From the video, the lineup was:

Mats Gustafsson-slide and baritone sax, conductor
Mariam Wallentin-voice
Anders Nyqvist-trumpets
Joe McPhee-trumpet, alto sax and space organ
Agustí Fernández-piano and organ
Kjell Nordeson-vibraphon
dieb13-turntables
Per Äke Holmlander-tuba
Jon Rune Strøm-bass
lngebrigt Håker Flaten-electric bass
Paal Nilssen-Love-drums

Hidros 8, subtitled Heal, was recorded in 2016 at DE Studio, in Antwerp, Belgium, on November 23rd, 2016, but not released on record until 2022 on Trost Records. Here the lineup was:

Anna Hogberg-alto saxophone, baritone saxophone
Mats Gustafsson-baritone saxophone, conduction
Susana Santos Silva-trumpet
Per Ake Holmlander-tuba
Hedvig Mollestad-guitar
Dieb13-turntables
Christof Kurzmann-lloopp, voice
Massimo Pupillo-bass
Gert-Jan Prins-drums, electronics
Ivar Loe Bjornstad-drums

A long break ensues until 2022, with Hidros 9, Mirrors, recorded at the Avant Art Festival, in Warsaw, Poland, on October 1st, 2022. Another large ensemble and very rich with electronics, this recording has Gustafsson only in the conduction role, but ably made up for by saxophonist Colin Stetson, and adding improvising rock guitarist Hedvig Mollestad to the mix.

Anders Nyqvist-trumpets
Colin Stetson-amplified bass saxophone
Hedvig Mollestad-guitar
Per-Ake Holmlander-tuba
Jerome Noetinger-revox tape machines
Dieb13-turntables
Mats Gustafsson-conductor
Eira Bjornstad Foss-violin
Matilda Rolfsson-bass drum
Lars Ove Fossheim-guitar
Michael F. Duch-bass
Ovind Engen-cello
Kyrre Laastad-drums, electronics
Nicolas Leirtro-bass
Daniel Formo-organ, prepared piano
Ida Lovli Hidle-accordion
Teoniki Rozynek-violin
Dominika Korzeniecka-bass drum
Szymon Wojcik-guitar, electronics
Rafal Rozalski-bass
Magdalena Bojanowicz-cello
Qba Janicki-drums, electronics
Pawel Romanczuk-bass
Barbara Drazkov-organ, prepared piano
Zbigniew Chojnacki-accordion

No doubt there are twists and turns that I've missed in my research, but I've been thrilled in my investigation as I've explored the evolution of Gustafsson's project. Last week we announced the latest Gush release with Sten Sandell and Raymond Strid, and the same week we added Hidros 9 we also added his EE Opus One album with his Ensemble E, another unique approach to unusual improv & contemporary ensembles. Alongside the many renderings of Fire!, his project with Johan Berthling, or The Thing with Ingebrigt Haker-Flaten and Paal Nilssen-Love, Gustafsson continues to be one of the most innovative and fascinating figures of the international improv community. Personally I'm eager for Hidros 10, and everything he releases inbetween!