All songs that have no tempo set at all should be queued on the background to have their tempo detected. The detected tempo should get stored in a separate field specific for the detected tempo, so that it doesn't overwrite anything. This new field should be considered in "primary mpm" for filtering purposes as the lowest priority. A tool for copying the detected tempo into a Manual or ID3 tag should be added.
All songs that have no tempo set at all should be queued on the background to have their tempo detected. The detected tempo should get stored in a separate field specific for the detected tempo, so that it doesn't overwrite anything. This new field should be considered in "primary mpm" for filtering purposes as the lowest priority. A tool for copying the detected tempo into a Manual or ID3 tag should be added.