Exclude single notes from ChordNames?

[sg2002]

Hello.

I've decided to learn a couple of songs on bayan, which is a Russian 
chromatic accordion.

Basic bayan bass parts often have a single bass notes followed by a 
chord, e. g.:

\new ChordNames {
   d \chordmode { d:m/a } f, q d q f, q  e, \chordmode { e:7^5/gis }  
gis, q e, q gis, q
 }

Since chords are often inverted and I'm not a proficient player by any 
means, having chord is nice. On the other hand I have no problems sight 
reading single notes. So ideally I want to exclude them from showing. 
For the example above that would mean only showing Dm and E7 chords.

Even better, I wish there was a way to get \set chordChanges = ##t 
working here, so that not only I would only see the names of real 
chords, but also only see them during changes.

Any tips? I had the idea of hacking a function that replaces single 
notes with rests, but maybe there's a simpler way?