He later took music classes, and joined the workers' choir "La Lyre des Travailleurs", founded by the socialist leader of Lille, Gustave Delory.

On 15 July 1888, Delory contacted Degeyter to compose music for several "Chants révolutionnaires" that were often sung at popular events with Lille socialists.

The lyrics had been written by Eugène Edine Pottier during the semaine sanglante (the "bloody week", May 22–28, 1871) marking the end and the severe repression of the Paris Commune of 1871.

The new composition was first played by the Lyre des Travailleurs at the yearly fête of the Lille trade union of newspaper sellers in July 1888.

At the beginning of 1916, however, during the First World War, Adolphe Degeyter hanged himself, leaving a note for his brother in which he acknowledged his fraud and asserted that he had been pressured by others to make the claim.

Pierre was invited to Moscow for the celebration of the 10th anniversary of the October Revolution and was in the stands of the honorary guests, with the German sculptor Käthe Kollwitz at his side.

As this was Pierre's only income, apart from modest fees collected on music for the other Pottier poems (particularly L'Insurgé and En avant la Classe Ouvrière) and on popular tunes he had also composed, and although the left-wing town administration of Saint-Denis granted him a free apartment, Pierre Degeyter spent the last years of his life in precarity.