Inconsistency in audio analysis for tracks with same ISRC

[Thajobe]

Hi,

I'm new to the spotify API.

As far as I understand, the ISRC code should uniquely identifying any sound.
I noticed, that there can be more than one track for a isrc at spotify. This happens for example when the same song is published multiple times:
e.g. the song with isrc "QZK6M2050645" was published as a single (id: 3VUxDjLowkVbLLAtTOu9AY) and as part of a album (id: 7w3SOC3cwLuTKKTUKO42XA).

When using the api to search for the isrc, only one track is returned. (In this case with id "7w3SOC3cwLuTKKTUKO42XA"). But you can verify, that the track with id "3VUxDjLowkVbLLAtTOu9AY" has the same isrc.

So far, so good. (Although, if all tracks would be returned, this would be nice.)

At least, we can be shure, that the audio data is the same for both ids, as they have the same isrc.

But, then I noted the following issue: If we assume, that the audio is the same, then the audio analysis should be the same too. However, this is not the case when retrieving the audi analysis for boths ids via the spotify api. The values are close to one another, but not identical (e.g. tempo 130.908 vs. 126.819). As far as I can tell from the meta information, both times the same analyzer ("analyzer_version": "4.0.0") was used.

Can any one explain what is going on? And if this is the expected behavior?

Best regards,
Jonathan