Introduction

If you’ve ever wished your Slack bot could talk back to you, you’re not alone. Adding voice responses turns a plain text interaction into a more engaging, accessible experience—perfect for status updates, alerts, or just a little fun. In this article we’ll walk through building a Slack bot that speaks using modern text‑to‑speech (TTS) and voice‑cloning technology. We’ll use ElevenLabs as the TTS engine (the affiliate link is included below) and glue everything together with a few lines of Python.

TL;DR – By the end of this guide you’ll have a Slack bot that receives a message, generates a realistic voice clip with ElevenLabs, uploads it to Slack, and posts the audio file back to the channel.

Why Voice in Slack?

  • Accessibility – Team members who are on the move or have visual impairments can listen to updates instead of reading them.
  • Speed – A quick “standup completed” audio clip can be processed faster than a long text thread.
  • Personality – A bot that sounds like a real person (or even a custom clone of your own voice) feels more human‑centric, which can improve adoption.

All of this is possible today without building a deep learning model from scratch. Services like ElevenLabs provide high‑quality, low‑latency TTS APIs that can even clone a voice from a few minutes of audio.

Getting Started with ElevenLabs

ElevenLabs offers a straightforward REST API for generating speech. Sign up through the affiliate link below, grab your API key, and you’re ready to go:

🔗 Try ElevenLabs here →

Once you have the key, you can request speech in a variety of voices, set speaking rates, and even use your own cloned voice model (if you’ve uploaded a sample). The API returns an MP3 stream that we’ll later upload to Slack.

Setting Up a Slack Bot

First, create a Slack app:

  1. Go to https://api.slack.com/apps and click Create New App.
  2. Choose From scratch, give it a name (e.g., VoiceBot), and select your workspace.
  3. Under OAuth & Permissions, add the following scopes:
    • chat:write
    • files:write
    • app_mentions:read
  4. Install the app to your workspace and copy the Bot User OAuth Token (it starts with xoxb-).

You’ll also need the Signing Secret under Basic Information for request verification.

Converting Text to Speech with ElevenLabs

Below is a minimal Python function that sends a prompt to ElevenLabs and returns the raw MP3 bytes.

import requests ELEVENLABS_API_KEY = "YOUR_ELEVENLABS_API_KEY" ELEVENLABS_TTS_URL = "https://api.elevenlabs.io/v1/text-to-speech/EXAMPLE_VOICE_ID" def synthesize_speech(text: str) -> bytes: """Call ElevenLabs TTS and return MP3 data.""" headers = { "xi-api-key": ELEVENLABS_API_KEY, "Content-Type": "application/json" } payload = { "text": text, "model_id": "eleven_monolingual_v1", "voice_settings": { "stability": 0.75, "similarity_boost": 0.85 } } response = requests.post(ELEVENLABS_TTS_URL, json=payload, headers=headers) response.raise_for_status() return response.content

Tip: Replace EXAMPLE_VOICE_ID with the ID of the voice you want to use. You can list your voices via the /v1/voices endpoint or use a cloned voice ID if you’ve uploaded a custom sample.

Uploading Audio to Slack

Slack doesn’t support streaming audio directly in a message, but you can upload an MP3 file and share it. Here’s a helper that takes the MP3 bytes from the previous step and posts it back to the channel where the bot was mentioned.

from slack_sdk import WebClient from slack_sdk.errors import SlackApiError SLACK_BOT_TOKEN = "xoxb-YOUR_SLACK_BOT_TOKEN" slack_client = WebClient(token=SLACK_BOT_TOKEN) def upload_and_post(audio_bytes: bytes, channel: str, title: str = "Voice reply"): try: # Upload the file first  upload_resp = slack_client.files_upload( channels=channel, file=audio_bytes, filename="reply.mp3", title=title, filetype="mp3" ) # Share the file in a message  slack_client.chat_postMessage( channel=channel, text=f"Here’s the voice response:", attachments=[ { "fallback": title, "title": title, "file_id": upload_resp["file"]["id"] } ] ) except SlackApiError as e: print(f"Slack error: {e.response['error']}")

Wiring It All Together

Now let’s create a simple Flask endpoint that Slack will hit whenever the bot is mentioned. The flow is:

  1. Slack sends an event_callback with the message text.
  2. Verify the request signature (omitted here for brevity).
  3. Strip the bot mention and feed the remaining text to synthesize_speech.
  4. Upload the MP3 back to the same channel. 
from flask import Flask, request, jsonify import hmac import hashlib import os app = Flask(__name__) SLACK_SIGNING_SECRET = os.getenv("SLACK_SIGNING_SECRET") def verify_slack_request(req): timestamp = req.headers.get("X-Slack-Request-Timestamp") sig_basestring = f"v0:{timestamp}:{req.get_data(as_text=True)}" my_sig = "v0=" + hmac.new( SLACK_SIGNING_SECRET.encode(), sig_basestring.encode(), hashlib.sha256 ).hexdigest() slack_sig = req.headers.get("X-Slack-Signature") return hmac.compare_digest(my_sig, slack_sig) @app.route("/slack/events", methods=["POST"]) def slack_events(): if not verify_slack_request(request): return "Invalid request", 403 data = request.json # Respond to URL verification challenge  if data.get("type") == "url_verification": return jsonify({"challenge": data["challenge"]}) # Only handle app_mention events  if data.get("event", {}).get("type") == "app_mention": event = data["event"] channel = event["channel"] user_text = event["text"] # Remove the bot mention part  cleaned_text = user_text.split(">")[1].strip() if ">" in user_text else user_text # Generate speech  audio = synthesize_speech(cleaned_text) # Post back to Slack  upload_and_post(audio, channel, title=f"Reply to <@{event['user']}>") return "", 200 if __name__ == "__main__": app.run(port=3000)

What you need to run this:

  • pip install flask slack_sdk requests
  • Set environment variables:
    • SLACK_SIGNING_SECRET
    • SLACK_BOT_TOKEN
    • ELEVENLABS_API_KEY

Expose the Flask server with a tool like ngrok and add the public URL to your Slack app’s Event Subscriptions (subscribe to app_mention).

Going Further

  • Voice Cloning – Upload a short audio sample to ElevenLabs, create a custom voice ID, and replace EXAMPLE_VOICE_ID with that ID. Your bot can now sound like your team lead, mascot, or even yourself.
  • Dynamic Parameters – Let users control speed, pitch, or emotion via slash commands (/voice speed=1.2 text=Hello).
  • Persisted Audio – Store generated clips in an S3 bucket and reuse them for frequently asked questions, saving API calls.

Next Steps

You now have a fully functional Slack bot that listens, converts text to a natural‑sounding voice, and replies with an audio file—all powered by ElevenLabs. Play around with different voices, experiment with voice cloning, and consider adding a UI in Slack to let users pick their favorite voice.

🔊 Ready to give your Slack bot a voice? Try ElevenLabs today and bring your bots to life: https://try.elevenlabs.io/kr07zfuqn1bp

Happy coding! 🚀