We have pre-exisisting midi files, that have now become 'transcodeable'. In order for the audio player to work however, it does need the derivatives, otherwise it has no source to play, as these are not generated on the fly.
Therefore cleanupTranscodes.php need to be run, so that these files can be put on the transcoding queue. The description file pages might have be be purge first, before the derivatives can be queued ?
Low priority, as files were not playable before and thus not widely used in articles and new files are automatically put on the queue. Manual queueing is possible by purging file description page and then manually triggering the transcode at the bottom of the page.