The original hymn MIDIs were provided to us by the Commission on Worship. Paul Grime generated them for us from the Finale files for each hymn, and set an "official" tempo for each one to give people an idea of a general speed at which each should be played. Paul's no longer serving as Executive Director of the CoW, though, and he's actually assisting with the production of a CD set we plan to release later this year containing recordings of every hymn and liturgy in LSB played on an organ. (This is for those congregations who are unable to find a musician.)
We go through our hymnal's editor to get access to these types of files. Peter (our hymnal editor) knows about this request, but has been busy with finishing the Music list for this year and also just went on paternity leave at the birth of his second child. We've talked about it on several occasions and unfortunately haven't had the opportunity to get it done.
It's pretty high on the "major things yet to get done" priority list for Builder. The controls are in place for those elements precisely because we've always planned on including the information at some point in the future.