The big problem with scientific instrument classification is that the Sachs-Hornbostel system (the one dealing with all the -phones)
only classifies instruments by exactly
what is vibrating. (Something always is if there's a sound.) In
this system, a chordophone has tense strings which somehow vibrate (whether the vibration is caused by it being struck, like a piano, plucked, like a harp, or bowed, like a violin,
falls outside the scope of this classification system). An ideophone is (instead of, as you say, 'vibrating instruments', which technically means every single instrument in existence) an instrument which produces sound by the vibration of some other material, be it wood, metal or something else, that is not a tense string or membrane. That means for example xylophone, marimba, and cymbals. Both a timpani and a gong is struck with a mallet of some kind, but the former is a membranophone and the latter an ideophone. This is enough to prove that this classification simply doesn't deal with how something is
caused to vibrate.
Let's take a look at the harp by this background. What vibrates? Strings under tension, of course. It's rather obvious that this makes it a chordophone. (That, though, does
not mean that it can't be percussion; see above.) You claim that it's also an ideophone. Is there any solid material involved, such as in a cymbal or a marimba? Not really.
While you could, and here I take back what I said earlier, call the harp a percussion instrument, why should you? No scientific classification system deals with it by how whatever vibrates is actually set into vibration (again, see above), so
percussion doesn't mean a lot there. Traditionally the harp is in the string section of an orchestra, and I doubt anyone would disagree on that.
From one thing to another, the trumpet stuff is a bit confusing. The partials, or harmonics, that you mention are all present in all instruments, but in varying amounts. From this scientific perspective no timbres are all that unsuited for each other.
I still don't get where fourths come in. The scale of a natural trumpet (which, if we get historical, is what we're talking about) is the harmonic series, not a bunch of fourths. All brass instruments work this way. (And, I might add, there are few tuning and scale systems that are not somehow based on the harmonic series.)
I don't think I'm taking this too far at all. If I was swearing at people and telling them that I am right because I say so, then I'd be a prick. But Eldkatt and I have been discussing this issue. Not because we hate each other, but because we are genuinely interested in each other's opinions. I'm sure Bach didn't care if it was a crapophone or not, but Eldkatt and I do.
It's great that we both agree here. I'm not a fan of annoying people--as long as you find this as interesting as I do, I can't see any problem. (This
is a discussion forum, isn't it?

)