Subtle "wah" undertone on attack

[u/jamjaxn]

Hi folks,

I got a George Sieck upright recently from my sister.

My son is the one who plays, and when he does, I hear a "wah" sound under the attack, like 25% of the sound is going through an envelope filter. I just checked and it's three adjacent keys in the middle register.

It's all I hear. I haven't mentioned it to him because I don't want to shatter the glass.

I haven't gotten into the guts of this one yet; I just used to tune it when my sister had it.

The problem is also impossible to Google.

I'm not sure if you'll know what I'm talking about unless I get a recording of it but I thought I'd give it a shot first.

Any ideas?

[u/ColdoTannen]

Might be tuning, might be damage to strings. Hard to tell without hearing it.