Hey Jozef,
You'll find an A minor seventh chord at the open position on your C6 neck. The root (A, of course) is 8th string open. You can voice it several different ways. I'll write the root on there, and you can use it if you want. I don't know if you use 3 or 4 picks.
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A minor A minor7th
1------------|----------------
2---0--------|--0--0--0-----0-
3---0---0----|--0-----0--0----
4---0---0--0-|--0--0--0-----0-
5------------|--0--0--0--0--0-
6-------0--0-|--0--------0----
7----------0-|--0-----------0-
8---0(root)--|--0--0-----0----
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For the Aminor 7th, there are so many possibilities, it would be hard to write them all out, but there are 5 of them anyway. The first one is strummed. The last two are my favourite, as they are voiced in what some call a "drop 1 voicing", taking the tone second from the top and dropping it an octave.
Just move it up the neck to suit. Another minor chord that's easy to get is by using pedal seven. In the open position, it's E minor.
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E minor E minor7th
1--------|--------
2--------|--------
3--------|--0(7)--
4---0(7)-|--0(7)--
5---0----|--0-----
6---0----|--0-----
7--------|--------
8--------|--------
9--------|-------
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The diminished chord, is usually played using the 5th and 6th pedals at the same time. They're everywhere!
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1--------
2--------
3--0-----
4--0-----
5--0(5)--
6--0(6)--
7--0-----
8--0-----
9--------
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You can also use the 2nd string sometimes, it provides one note from the diminished scale that isn't amongst the others (which are stacks of minor thirds)
Remember, every diminished voicing is
four diminished chords. In this example, it's C, Eb, Gb, and/or A diminished. Also remember that every diminished voicing is also
four 7b9
chords. In our example, they are D, F, Ab, and B 7b9.
Ok, I'm babbling
hope this helps.
-John