Diatonic Chords

{
  "asOf": "2026-10-12T01:46:28.079Z",
  "chords": [
    {
      "degree": 1,
      "roman": "I",
      "seventh": "Cmaj7",
      "seventhNotes": [
        "C",
        "E",
        "…2 more"
      ],
      "triad": "C",
      "triadNotes": [
        "C",
        "E",
        "…1 more"
      ],
      "triadQuality": "major"
    },
    {
      "degree": 2,
      "roman": "ii",
      "seventh": "Dm7",
      "seventhNotes": [
        "D",
        "F",
        "…2 more"
      ],
      "triad": "Dm",
      "triadNotes": [
        "D",
        "F",
        "…1 more"
      ],
      "triadQuality": "minor"
    }
  ],
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "key": "C major",
  "notChecked": [
    "chords borrowed from other keys or modes, and secondary dominants",
    "modes beyond major, natural minor and harmonic minor (melodic minor and church modes)",
    "…1 more"
  ],
  "reasons": [
    "Each chord stacks the scale degrees a third apart (1-3-5, then 7), so the spelling follows the scale and never uses an enharmonic respelling.",
    "Lower-case numerals are minor or diminished, upper-case are major."
  ],
  "scaleNotes": [
    "C",
    "D",
    "…5 more"
  ],
  "scaleUsed": "major",
  "signature": "no sharps or flats",
  "source": "computed locally (stacked thirds on each scale degree; each note keeps its own letter name)",
  "summary": "C major, major scale: C Dm Em F G Am Bdim.",
  "verdict": "COMPUTED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://music-production-calc.x402tookit.com/diatonic-chords?key=C'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://music-production-calc.x402tookit.com/diatonic-chords?key=C' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fmusic-production-calc.x402tookit.com%2Fdiatonic-chords
const res = await pay("https://music-production-calc.x402tookit.com/diatonic-chords?key=C");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://music-production-calc.x402tookit.com/diatonic-chords?key=C")
    print(res.status_code, res.text)