Haralds Arnis became passionate about music at an early age. At the age of 5, he started his musical career at the Emīls Dārziņš Music School, playing the piano. At the age of 11, he started playing the double bass. He studied instruments with Einars Upatnieks all his years at music school. After graduating from the Emīls Dārziņš music school in 2020, Haralds studies at the Jāzeps Vītolas Latvian Music Academy with Sergejs Brīnums. In the ERASMUS exchange program, he went to the Czech Republic to expand his experience (instructor Miloslav Jelinek). Haralds Arnis gained orchestral experience by working in the Latvian National Opera and Ballet Orchestra and continues to play with passion in various ensembles and chamber ensembles.

Since 2023, he has been a musician of the Sinfonietta Riga double bass group.