Building up an arp pattern in normal (non-hold) mode on the UDO is in the expected way, the arp only picks up the notes you’re actually holding down with your fingers.
However, building up an arp pattern in key-hold mode is not the way I’m used to. Why? Because the arp still expects me to hold down the notes with my fingers, despite the fact that Hold is enabled. This limits the range of notes I’d like to add, as the reach of my hands goes only so far. And the constant stretching is fatiguing.
Here’s how I’d like the arp to work in key-hold mode:
- Press down the first key, and do not release it until you want to clear the arp pattern and start over.
- Extend the arp pattern by playing other keys. Simply play and release them (with one finger if you like), the arp will pick them up anyway. (The first key still being held down.)
- If you want to go for a really low, or really high note, go ahead and use the keyboard range toggle and hit the note you’re after. (The first key still being held down).
- Enjoy your arp, and add more notes over time, after a couple of bars, one by one, like building up a sequence in real time. (The first key still being held down).
- When ready for something new, release everything, including that first key you still held down in step 1, and build a new pattern.
EDIT: holding down any other key of the pattern to keep it going, instead of the first key also works.
This is how the Key Step Pro works, and a number of other synths I’ve been using for arps.