One of the ways I practise improvisation is by creating short, complete pieces which are under two minutes long. No timer is running; the aim is to judge the time as well as the musical material to create the piece within the time limit. This forces you to communicate your ideas directly; you don't have 5 minutes for vague development. It is an exercise in brevity.
Themes are thought of on the spur of the moment; this improvisation uses lilting 3rds to drive a crescendo from the 8' flutes to full organ.
Further information about the 1965 Downes/Walker organ of the Carmelite Priory, London can be found here:
https://www.carmelitechoir.com/organ/
Although modest in size and somewhat quirky, the scheme is exceptionally cohesive and, helped by the Priory's wonderful acoustic, gives the impression of a much larger instrument.
Recorded with Oktava MK 012 omni microphones and a Zoom Q8.
http://www.simon-lloyd.com