NOTICE: You will either have to use the talk page to explain your question, or rephrase the question. It is vague on what you mean by "Series"
Vocaloid is the first series, often referred to in the fandom as "Vocaloid 1", "Vocaloid series 1" or "V1".
The earliest hint of a song series is the "Aku no" Series" later growing to be "The Evillious Chronicles", in the year 2008 and as early as February. These are headed by mothy(AkunoP), a Japanese producer.