Most of the bandsmen are homecasts of the Red Army Infantry figure from Britains set 2032. The original figure has two shoulder pegs for the May Day Parade pose of rifle extended in front. This makes it a natural for conversion to a musician-holding-instrument pose. The side drummer is a little more complicated conversions, and the bass drummer and drum major are standard Britains figures with new heads.
Why say homecast? On the underside of the base, there are signs of two rectangular sprue gates, neatly placed at the bottom of each foot, right where Britains also had them - the larger circular spots on original bases, only one of which is visible on the casting photo. The half-cast bottom of the base is another clue. The odd angled cut of the base by each foot is in the original design. This was a new figure introduced in 1949, not used for any other set.
This band is a brilliant conversion, giving the necessary accompaniment for a proper May Day parade scene.