Rootless voicings are pretty common in jazz, especially when playing with a bassist. With a dominant 7, specifically, it's also common to also omit the 5th, and just play the color notes (3rd, 7th, 9th... throw in a 13th if you'd like). There are much better jazz players on this forum that could probably elaborate on this and/or correct me, but that's my best guess why it inferred a C9.

Yes, that does make sense. It's interesting to see where they're coming from with chord interpretations. Most of the time I don't take any notice of the chord display TBH, but occasionally I see it come up with something that makes me think 'Huh? How did it get that?'

I do think it's a bit odd that it names it as C9 without having the root note present.

Thank you.

Yes, the root chord's absence was the main source of my confusion, so something I'll know to watch out for in future.  Useful info.

I was playing around last night and my interest was drawn to a combination of three notes (using them in the left hand) which were E, Bb and D.

Pianoteq identifies these as a C9 chord (just those three notes played !) and while, yes, those notes are in a C9 surely that's not the correct name for that set of notes ?  Pianoteq does also identify the full C9 chord correctly, BTW.

On online chord identifier came up with E7b5sus (which is new territory for me).

So is Pianoteq wrong in naming it this way or am I simply misunderstanding the chord naming conventions (good odds on that last one) ?

Thanks in advance.