During the 1960s, Kalniņš led the Liepāja rock band 2xBBM, which was extremely loved because of its heartfelt songs and hippy-like lifestyle.

Kalniņš became the symbol of the spirituality, rebellion and worldview of the generation, and it was emphasized by the fact the band was forced to stop playing because of the pressure from official institutions.

The festival most associated with Kalniņš is the Imantdienas ('The Days of Imants'), extremely popular during the Soviet times and therefore banned.

The tradition was reintroduced in 1995, and since then has happened every year (with the exception of 1997, when the composer was away on a trip, and 2009 after the 2008 Latvian financial crisis).

[lv], and their collaboration has resulted in some albums containing primarily music by Kalniņš, such as Par lietām, kas tā ar' nekad nepāriet (About things that never truly go away) (1997), Es redzēju sapnī (I Saw in a dream) (1998) and I Love You (1999; despite the English title, the lyrics are mostly in Latvian in this album).

They had three children, Dana Kalniņa-Zaķe who became the lead for the Latvian Association of Professional Health Care Chaplains, actress Rēzija Kalniņa and pastor Krists Kalniņš.