After a successful run of over 10 years, our MIDI playing app Rondo, has been discontinued. It still works on recent operating systems but is getting really long in the tooth and is proving impossible to update. There are vague plans for a rewrite but it could be a while. Many thanks to all the people that purchased Rondo over the years.
Rondo is still available for download from here.
UPDATE May 2018: Rondo appears to work fine on all MacOS versions from at least 10.7 up to the current 10.13.4