The Rudolf Steiner Archive is here: they may know something: 
https://wn.rsarchive.org/Lectures/GA278/English/AMTRP1996/EuViSg_index.html
     Rudolf at least wrote about music, and several schools use his 
'methods?'

On 4/12/2019 11:15 AM, Railroads On Parade wrote:
> Has anyone ever seen a Pathe disc X No.93.049 (listed in the W.E.R.M.) of
> Schubert sung by Rudolf Steiner?   For those vocal record enthusiasts,
> Lawrence Holdridge has told me he's never heard of a singer named Rudolf
> Steiner, only Fritz Steiner.
> Right now I've emailed EMI to see if they have any info on the creation of
> this recording, and I've got the ear of the Library of Congress as well.
> It is my contention this must be a posthumous production of the
> anthroposophist from an acetate produced using a transcription recording
> machine around the early '20s and then handed off to Pathe in 1930 or '31.
> Is this technologically possible?
>
> ---
> This email has been checked for viruses by AVG.
> https://www.avg.com
>