I was attempting to link https://www.operabase.com/o10152 to https://musicbrainz.org/artist/5b13c665-88eb-4e80-9a06-218a660fcf6b but got an error:

This URL is not allowed for the selected link type, or is incorrectly formatted.

It seems that this is due to the "o" in the link, rather than "a": https://www.operabase.com/a10152 passes is not flagged by the editor. However, it resolves to a different artist.

It seems as if "o###" is intended as an identifier for organisations.

For example, some orchestras:

• https://www.operabase.com/bbc-symphony-orchestra-o10152/en
• https://www.operabase.com/new-york-philharmonic-o14745/en
• https://www.operabase.com/st-petersburg-philharmonic-o30287/en

And opera companies

• https://www.operabase.com/istrian-national-theatre-pula-o21110/en
• https://www.operabase.com/en-opera-o9643/en

There is at least one orchestra listed twice.  Once with "a###" and once with "o###":

• https://www.operabase.com/bbc-scottish-symphony-orchestra-a2251638/en
• https://www.operabase.com/bbc-scottish-symphony-orchestra-o10151/en