So it turns out the motion smoothing / slide effect only occurs when sequencing pitch changes on the Volca Drum itself, even if a new pitch is set per step in Step Edit Mode. So the motion sequencer seems to be adding interpolated pitch movement between steps. @OscillatorSink describes this in the comments thread for his Using the Korg Drum Melodically - Part 1 YouTube video.
However, as demonstrated by Retrokits (on Instagram here & here, or Twitter here & here, or Facebook here & here), if you turn on the new pitch quantization feature and have a way to assign MIDI notes to different values for MIDI CC 28 (to set the pitch of both layers 1 & 2 of one drum part, with the Volcas Drum in split channel mode), then external sequencing of melodic play doesn’t have the slide / portamento effect.
If using Retrokits’ RK-002 Smart MIDI Cable, they have taken the method of assigning notes for melodic play takes it one step further by adding polyphonic MIDI chaining, with their Volca Drum MIDI Expander firmware app for the RK-002. Using their special PolyMUX method, this firmware allows the RK-002 to spread up to 6 notes played polyphonically from a single MIDI keyboard across the 6 parts of the Volca Drum. Or, as their demo videos show, mix a combination of external polyphonic note sequences synced with a percussive sequence on the Volca Drum itself, using the remaining unused parts.
Additionally, although Retrokits hasn’t yet implemented it in an RK-002 firmware app, in theory the two individual layers of a drum part could play different notes, allowing up to 12 note polyphony, but only with the somewhat “simpler” sounds that a single layer would offer.
I own an RK-002, which I’ve used for melodic polyphonic play on my Volca Sample, but I haven’t tried out this new RK-002 firmware app for the Volca Drum yet, so I’d like to note one other important thing, as observed by @OscillatorSink over on his YouTube channel:
To turn on pitch quantization, you need to be in Edit mode; twist the select knob like you would for bit-crush, folding etc. and at the end you’ll see “QPI” - turn that bad boy on!
Now, for that part, when you twist the pitch knob you’ll see pitches rather than numbers! However - the pitches shown don’t seem to be accurate all the time, even relative to each other (C4 and G5 are an octave apart for me?).
In spite of that, the intervals are generally more musical and pleasing, so if you’re tuning my ear, it seems to be loads easier to get things to sound “in tune”. So ignore what you’re seeing and use your ears.
Update: the pitch weirdness… …seems to be something to do with using the Layer 1-2 editing. If you’re just editing Layer 1 or 2 on its own, the tuning looks good!
He doesn’t mention whether the strange pitch tuning that only occurs when editing layer 1/2 together also applies to MIDI CC control, so I’m not sure that will effect the RK-002 solution for melodic play (or other similar solutions people may come up with.)
All in all, this is fantastic news, though! I am really looking forward to messing around with melodic sound design on the Volca Drum and playing notes using my RK-002. I will post any of my findings here when I have a chance.
I also highly highly suggest subscribing to @OscillatorSink’s YouTube channel because he is planning on doing a Part 2 video on Melodic Play on the Volca Drum and will likely cover all of the ins and outs and considerations for using it in that way.