One line of text. One line of sound. Click to hear this headline · voice en-heart · unedited API output

Five voices, two engines. Each one is exactly what it is.

Kokoro (Apache-2.0) for English, Piper (MIT) for German. No cloning, no "make it sound like X" — that door stays closed on purpose.

curl -X POST https://klangzeile.com/v1/tts \
  -H "Authorization: Bearer sk_live_…" \
  -H "Idempotency-Key: order-4711-confirmed" \
  -H "Content-Type: application/json" \
  -d '{"text": "Your order is on its way.", "voice": "en-heart", "format": "mp3"}' \
  -o confirmation.mp3

# response headers
Content-Type: audio/mpeg
X-Characters-Billed: 25

import httpx

r = httpx.post("https://klangzeile.com/v1/tts",
    headers={"Authorization": "Bearer sk_live_…",
             "Idempotency-Key": "order-4711-confirmed"},
    json={"text": "Your order is on its way.",
          "voice": "en-heart", "format": "mp3"})
r.raise_for_status()
open("confirmation.mp3", "wb").write(r.content)
print(r.headers["X-Characters-Billed"])  # 25

const r = await fetch("https://klangzeile.com/v1/tts", {
  method: "POST",
  headers: { Authorization: "Bearer sk_live_…",
             "Idempotency-Key": "order-4711-confirmed",
             "Content-Type": "application/json" },
  body: JSON.stringify({ text: "Your order is on its way.",
                         voice: "en-heart", format: "mp3" })
});
if (!r.ok) throw await r.json();   // RFC 7807 problem+json, with request_id
const audio = new Audio(URL.createObjectURL(await r.blob()));
audio.play();

• Nothing is stored.Text in, audio out. What remains is a character count and a SHA-256 of the request — no text, no audio, no logs with content.
• No voice cloning.Five fixed voices under permissive licences. We will not build a "sound like anyone" feature.
• Hosted in Germany.Servers in Nuremberg. No third-party AI providers behind the API; the models run on our machines.
• Pinned engines.Kokoro 82M v1.0 and Piper are version-pinned by hash. The same text gives the same audio until we say otherwise.
• Limits, not surprises.When the monthly quota is used up the API answers 402. Overage is never billed.
• Boring, on purpose.Bearer keys, JSON, standard headers. Nothing to install, nothing to learn twice.

Need more than a million characters, or an invoice instead of a card? Write to us.