Niemack eventually moved to New York City in 1977, her first major engagement was a week at the Village Vanguard, singing in Warne Marsh's band.

[1] Her debut album, By Heart was recorded in New York City and released in 1977; since then she has recorded 12 albums under her own name in addition to working with Toots Thielemans, James Moody, Lee Konitz, Clark Terry, Kenny Barron, Fred Hersch, Kenny Werner, Joe Lovano, Eddie Gómez and the WDR Big Band (among others).

[2] In 1987, while living in New York, Niemack met guitarist Jeanfrançois Prins; the two would eventually marry in 1998.

Prominent vocal students of Niemack's include artists such as Dominique Lacasa, Marc Secara, Efrat Alony, Lucia Cadotsch and Erik Leuthäuser.

Niemack has written lyrics for over 100 compositions by Thelonious Monk, Bill Evans, Richie Beirach, Pat Metheny and Kenny Dorham (among others) which have been recorded on numerous albums.