Lehto has studied flute at the Turku Conservatory and the Sibelius Academy, and has played with the Navy Band , Turku Philharmonic Orchestra and since 1987 at the Pori Sinfonietta . In addition, Lehto has worked as a music teacher in Uusikaupunki , where he also conducted Crusell Week .
Lehto has composed music for flute and wind orchestra since the mid-1990s and, in recent years, for string and symphony orchestras as well as for various chamber ensembles. His works have been performed abroad, including in Hungary, the United States, England and Japan. Lehto's flute-piano works include Air (1996) and Fusion (2001).
In 2009, Lehto won the Ciutat de Betera Composition Competition in Spain for his work Cur .  In 2014, he won the Windstream 2014 Competition in Riga for his composition Motus contrarius .  In the same year he also won the Satakunta Art Award.