This is the mame pgmusic gives to these chords:

Tricky Chords:

C5b This is "C flat 5." It is spelled this way to avoid confusion.

C2, C5, C4, C69, C7alt, Cm7#5

I know C5 chords of course, so-called "powerchords"

but not the other chords

did you see/used any of them in a pop song ?

what feeling do they give you in your mind ?

thanks,
Bernard

Lets see if you can hear this...?

C2, C5, C4, C69, C7alt, Cm7#5 in Scaler 2

Opps I played the incorrect last chord. If this helps I can redo it. Use any program (Scaler 2 or Pianoteq 7) which allows you to play or type any chord to record the midi so you can hear it. Generally chord voicing along with the harmony would make or break the sound of these altered chords.

Dan's midi sounds like C7alt and Cm7#5 are jazz chords, but a different timbre might put them into some pretty dissonant rock territory. I've used them in experimenting. The "feeling" is hard to describe. I have a high tolerance for dissonance.

C2 and C4 are just other ways to spell Csus2 and Csus4, I THINK. They are in every kind of music. The feeling is kind of an emotional reach or longing. The C4 evokes that more strongly, the C2 less strongly. When they resolve to the normal triad, it feels like a sigh. Breathe in, breathe out.

C5 is a power chord. It leaves out the 3rd, so there is no obvious MAJOR or MINOR tonality. So it's ambiguous by design. I think "power" is probably the right word for the feeling evoked, but it's like the power of a cloud or a tree, rather than a hammer..

C69 is sort of a less "Bluesy", more "jazzy" version of a dominant 7th--C7. On the other hand, it's also the more grown up version of a CMaj7--still some spice, but smoother. If it were a candy, it would be dark chocolate and sea salt. It's the 9 that adds the touch of spice/salt, and the 6 the not-too-sweet sweetness. I've used them, because I have to use everything I learn about. And, of course, because I'm naughty. But I think they are fairly uncommon and situational.

All of the above is purely subjective.

Load 'em up into BIAB. Precede them all with the C triad to reset your ears a bit. What do get out of them?

I would agree, in terms of a triad little more then just removing the 3rd and replacing it with a 2nd or 4th, respectively. However, I did inadvertently jazz them up a bit. The C5 is just root and fifth in my example.

A few random comments.

m7(b5) is far more common than #5 and is called a half-diminished chord.

A 2 chord in BIAB is used for several chords: add2, add9, and as noted, sus2. However, in pure music theory sus2 is rather discouraged as it is not really a suspended chord in the sense that, where does it resolve? But I know this will start an argument so never mind. If you look at the file pgshortc.txt you will see how BIAB uses the 2 chord. ps I do not agree.

A 6/9 chord is one of the most magical sounds in the world when played on a Bossa Nova acoustic guitar. Musically it is in the same grouping as a major triad and major seventh, in the sense that jazz players use these three interchangeably.

Finally, while a 7alt chord is a jazz staple, you May find it as the final chord in a four or eight bar phrase in pop songs. The ‘alt’ means altered. That means that the fifth is not perfect and the ninth is not major. Thus the chord may have any combination of flat or sharp 5, and / or flat or sharp 9.

Hope that helps.

one thing i discovered years ago as a guitarist is that moving a finger, or adding an extra note is often dead easy and sounds cool but results in a chord with an extremely complicated name. when i know what i play on a guitar i often have to look up on a chord site to find the name of what i'm playing. one riff that sounds cool is an A minor shape slid up two frets then down again leaving the E,A and top E strings open. i'm told that's a Bm11/E. sounds good on a guitar never tried it in BIAB.

just about any chord within reason will sound good in the right place but you need real musical expertise like Matt's to know what to enter in BIAB without a lot of trial and error.

Yep. Also remember a 3 or 4 fingered guitar chord can have a number of different chord names. Here are a couple of web sites that I use to determine the names of such chords:

https://www.oolimo.com/guitarchords/find

https://www.oolimo.com/guitarchords/analyze

And if you can play the chord on a MIDI keyboard, BIAB will give you up to four suggestions what it is. Windows menu, MIDI Chord Detection. I rarely need to go to a third party but like Mario, I use them too.

Also, in the chord builder window, you can sound all the possible chords (on the piano patch) and decide for yourself. Learn what every chord sounds like. Not easy …

The voicing and/or inversion matters. A 9 and a 2 are the same note, but the more distance between the 2 and the 1, the less dissonance. A Cadd9 has a different feeling than a C9.

Pretty much any chord naming beyond triads and maybe 7ths can often be spelled more ways than one.

I think guitar players (including myself, though I'm more of a guitar banger) think of chords as entities in themselves and the "skill", beyond learning how to make them, is in learning how to make them in other ways, and in embellishing them. I think this is less true of keyboard players. I think they 'think' of chords more correctly as assemblages of notes/intervals played--not just in blocks but also broken up. Chord names are for communication and/or analysis.

Those are over-generalizations, and there's value in both approaches in the differing instruments.

Bernard's question about the "feelings" invoked by these collections of intervals is a great one. If we are creating our own chord progressions, it can be really helpful to assign an emotion or flavor to the various chord types. On guitar, in open position, I'll sometimes play an Fmaj7 instead of an Am because that's the "feeling" I want to convey...wistful over sad...at least that's the way I hear it. The "fingering" is very close on guitar in the open position. That might not mean much to a piano player.

wow, thank you so much to everyone who gave an answer
this is a fascinating subject
I did not learn a lot of conventional harmony
So I tend to think of chords as colors, flavors or feelings
and in any case, as the basic building blocks of any piece of music
but this is only my "gut feeling"