Roman Numerals

{
  "analysis": [
    {
      "chord": "C",
      "degreeFromTonic": 0,
      "diatonic": true,
      "diatonicNote": "diatonic to the major scale",
      "numeral": "I",
      "role": "tonic",
      "root": "C"
    },
    {
      "chord": "Am",
      "degreeFromTonic": 9,
      "diatonic": true,
      "diatonicNote": "diatonic to the major scale",
      "numeral": "vi",
      "role": "tonic substitute",
      "root": "A"
    }
  ],
  "asOf": "2026-10-11T14:26:14.523Z",
  "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": [
    "modulations and tonicisations beyond one-step secondary dominants",
    "modal mixture other than the natural and harmonic minor (other chords are labelled borrowed or altered)",
    "…1 more"
  ],
  "numerals": [
    "I",
    "vi",
    "…2 more"
  ],
  "reasons": [
    "Uppercase = major (or dominant), lowercase = minor or diminished; ° diminished, ø half-diminished, + augmented; 6, 64, 65, 43, 42 mark inversions from a slash bass.",
    "In a minor key the natural minor scale is the reference; the major V, V7 and the diminished vii° are also accepted as harmonic minor."
  ],
  "source": "computed locally",
  "summary": "In C major: I vi IV V7.",
  "verdict": "ALL_DIATONIC"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://music-theory.x402tookit.com/roman-numerals?key=C&progression=C+Am+F+G7'

# 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-theory.x402tookit.com/roman-numerals?key=C&progression=C+Am+F+G7' \
  | 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-theory.x402tookit.com%2Froman-numerals
const res = await pay("https://music-theory.x402tookit.com/roman-numerals?key=C&progression=C+Am+F+G7");
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-theory.x402tookit.com/roman-numerals?key=C&progression=C+Am+F+G7")
    print(res.status_code, res.text)