What does 70 bpm mean in Mixed in Key?

[zujar_man]

Every now and then I get an oddly low number for the BPM when using the software tool 'Mixed in Key'.

Lists the BPM as 70 but it's more like 140++. Can't find anything about it, so can someone clarifiy?

Cheers

[albertus]

70 is obviously exactly half of 140. It's easy to argue that a track in the tempo of 140 could be seen as a track in the tempo of 70, just with notes that are half the length (i.e., a bassdrum kicking in eights instead of quarters).
For this reason, many BPM detection algorithms need to be given a range, such as "90 - 179", which does not contain any pair of numbers with one being a multiple of the other.