The free market
The only possibility for a jazz musician to have a permanent position is whith the Metropole Orkest. So jazz musicians who want to build up a career as perfoming musicians have to play a lot, and in many various groupings. The strong desire for innovation which is so characteristic of Dutch jazz means that music is regularly created and played in unusual and adventurous combinations. This is why there are so many jazz groups in both large and small groupings which all want to perform as much as possible.
In the classical sector many musicians have jobs in orchestras in addition to the various ensembles, which creates more of an ad hoc culture within the ensembles. Most pop groups only become professional after commercial success; before that their music is commonly practiced in their spare time. But most jazz ensembles, certainly the ones which aren’t subsidized, keep going tirelessly throughout the year.
Of course there are also ad hoc formations within the jazz world which are brought together for special projects (often supported by project subsidies). It is estimated that there are around 500 ensembles and soloists working in the free market. There are about 1500 musicians active in the area of jazz and improvisational music.