Converting MTD files into scores via midi

In order to learn all the voices of a choral, I produce WAV files in which one singer is placed on the left, the others to the right. Doing this alternatively for all voices (SATB) allows me to pick up the voices one by one.

As I am not very good at reading notes, I have to get the original score into MuseScore, in order to perform this manipulation of the sound file. This is why I would like to convert MTD files (MusicScore's proprietory format) into MuseScore files. I have bought the MTD file beforehand, so I assume this to be totally legal as long as I do this for my own purpose.

I used Midi Yoke to redirect the midi output of the MusicScore play/print software to MuseScore. This works fine, only that the notes all have the same duration. The notes are placed on one staff (there is obviously only a single midi instrument in the MTD file) and after editing them, I place them on four staves by means of the Explode plugin.

I tried to save some work by recording the midi output with Midi-Ox and converting it to midi by means of T2MF. This basically worked, including note durations, but produced slightly false note durations, like having been recorded live on a keyboard. (I know this feature doesn't exist in MuseScore, but I have experience with other programs.)

Any ideas what went wrong or how to perform the task with less editing effort? Any suggestions are welcome!