When he and Heinonen started at Suutarila high school in the early 1990s, they met Pauli Rantasalmi and later Janne Heiskanen. Ylönen initiated the project of The Rasmus (then called just "Rasmus") in 1994, along with Eero Heinonen (bass) Pauli Rantasalmi (guitar), and Jarno Lahti (drums), with Lahti subsequently being replaced by Heiskanen. First, they called themselves Trashmosh, then Anttila, and at last Rasmus. They played their very first show before the winter break in school, 1994. They played songs with a style of rock and funk. Ylönen became the lead singer, composer and songwriter of the band. He quit school because the band took too much of his time.