After Petter died in 1871, Karl purchased his share of the business and became the company's sole owner.
[1] In 1880 Hals opened their own public concert hall which was known for its excellent acoustics.
In 1886 the company began building harmoniums in addition to pianos, and in 1887 they expanded into music publishing after acquiring Petter Håkonsen's music publishing business.
[1] The music publishing part of Hals ceased operation in 1909 when it merged with Carl Warmuth's music publishing firm to form Norsk Musikforlag.
In 1925 the piano manufacturing part of the business was sold and absorbed into Grøndahl & Søn.