The May Day matinée is a tradition introduced by Robert Kajanus and has continued right up to the present day. A popular concert was held as early as May Day 1883, but that in 1884 was advertised specifically as one for May Day morning.
The first matinées were held at the Fire Station Hall, the Seurahuone (‘Assembly Rooms’, nowadays Helsinki City Hall) or the Kaivohuone, which over the years came to be the regular venue. In the 1940s the May Day matinée was as a rule held at the Conservatory, before transferring in time to Finlandia Hall.
The repertoire for this May Day concert has not seen any radical changes with the passing of the decades; the March of the Men of Pori, for example, has been a regular item ever since 1889. The overture to Wagner’s Lohengrin has been played at least since the beginning of the 20th century, and almost every concert has included something by Sibelius. The arrangement by Arthur Fuhrmann of the tango Uno by Mariano Mores became a fixed item on the programme in 1976.
Sources: Concert details for the Helsinki Philharmonic Orchestra, Opas database, Anu Fagerström & National Library, digitalised newspapers