Max Reger. Orgelsonaten
Erste Sonate op. 33

https://www.youtube.com/watch?v=swPdVADGHmg (First part only) - Iveta Apkalna

https://www.youtube.com/watch?v=v-JN8OfxdPc (Complete sonata)

The first part is the most interesting one. The last part, Passacaglia, is quite similar to Reger's most well known Introduktion und Passacaglia.

https://youtu.be/ZWNo-F7Jyms?t=135


Zweite Sonate op. 60

https://www.youtube.com/watch?v=vMzUOyQllWU - Martin Sander. Very good performance.


Never heard of Iveta Apkalna, but her interpretation was good.
What else I could find by Apkalna:

https://www.youtube.com/watch?v=AOkrLX-i5bE Kalējs - Allein Gott in der Hoh sei Ehr (Iveta Apkalna, organ)