We've (in the royal sense) just pressed the release button at Apple on a new version of the MidiBus app.
This mainly adds a new feature that allows you to use an external MIDI controller to 'tap' the tempo even while the clock is running.
It works by 'learning' the event you wish to use to set the tempo. Here's how to do it:
1. Make sure that the controller you want to use is being monitored. On the Monitor panel in the app check that the connected controller (can be another app, hardware or wifi/bluetooth port) has a blue arrow/clock icon (not red X).
2. Flip to the Transport panel and press the 'bpm' field to expand the Tap Tempo controls.
3. Slide the 'learn' switch to 'On' and generate your external MIDI event that you wish to use to control the tempo. The event must be either a note, controller (value > 0) or a program change. Once the learn function has seen one of these events it remembers that event as the tap tempo trigger (hex value of learnt event shown in the textfield) and automatically switches out of learn mode.
Subsequent taps of the learn event will set the tempo of the clock signal. You can do this while the clock is running (this applies to the 'Tap Tempo' button in the app too in this release. The learnt event is channelised in that subsequent events must be on the same channel as the learnt event to trigger the tempo adjustment.
This release also adds support for a forthcoming companion app to the MidiBus Clock app. More details will follow when that is released.