As I've started to realize a piano transcription of M4' finale, that I wish to be the closest possible to Mahler's version, I often listen to his "recording" on the Welte Mignon rolls.
For those who want to get familiarized with the Welte Mignon system, there are very detailed explanations with photographs on the Tacet website:
http://www.tacet.de/main/seite1.php?language=en&filename=welte.php&layout=katalogSo the more I listen to, the more I become aware of the importance of this testimony to get an idea about how Mahler could be as a musician, a conductor and as a person. I like the charm , the spontaneity, the natural and the vivacity of his playing. The way he phrases the beginning is delightful. I'll enjoy playing Mahler with Mahler when I finish the job.
I've ordered the Preiser Records CD "Gustav Mahler und sein Klavier".The samples I heard sounded very clear, especially the left hand. (useful for me). I didn't understand if the reproduction was done on Mahler's own Blüthner piano, or on a Blüthner as Mahler's one. The CD notes will probably clear this point.
The Kaplan Collection record probably sounds well too. Who knows it?