When you submit a task to the Add Vocals API, you can use the callBackUrl parameter to set a callback URL. When the task is completed, the system will automatically push the results to your specified address.

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Callback Mechanism Overview

The callback mechanism eliminates the need to poll the API for task status. The system will proactively push task completion results to your server.

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Callback Timing

The system will send callback notifications in the following situations:
  • Text generation completed (text stage)
  • First vocal track generated (first stage)
  • All vocal tracks generated (complete stage)
  • Vocal generation task failed
  • Error occurred during task processing

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Callback Method

  • HTTP Method: POST
  • Content Type: application/json
  • Timeout: 15 seconds

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Callback Request Format

When the task is completed, the system will send a POST request to your callBackUrl in the following format: 
{
  "code": 200,
  "msg": "Text generation completed successfully.",
  "data": {
    "callbackType": "text",
    "task_id": "2fac****9f72",
    "data": []
  }
}

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Status Code Description

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code
integer
required
Callback status code indicating task processing result:
Status CodeDescription
200Success - Vocal generation completed
400Bad Request - Parameter error or content violation
401Unauthorized - Invalid API key
413Content Too Long - Prompt or style description exceeds limit
429Insufficient Credits - Account credit balance insufficient
500Server Error - Please retry later
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msg
string
required
Status message providing detailed status description
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data.callbackType
string
required
Callback type indicating the current callback stage:
  • text: Text generation completed
  • first: First vocal track generated
  • complete: All vocal tracks generated
  • failed: Task failed
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data.task_id
string
required
Task ID, consistent with the taskId returned when you submitted the task
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data.data
array
Vocal generation result information, returned on success
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data.data[].id
string
Audio unique identifier (audioId)
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data.data[].audio_url
string
Audio file download link with vocals
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data.data[].source_audio_url
string
Original source audio file download link
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data.data[].stream_audio_url
string
Streaming audio playback link with vocals
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data.data[].image_url
string
Music cover image link
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data.data[].prompt
string
Prompt/lyrics used for vocal generation
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data.data[].model_name
string
AI model name used for vocal generation
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data.data[].title
string
Music title with vocals
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data.data[].tags
string
Music style tags including vocal characteristics
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data.data[].createTime
string
Creation time
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data.data[].duration
number
Audio duration (seconds)

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Callback Reception Examples

Here are example codes for receiving callbacks in various popular programming languages: 
const express = require('express');
const app = express();

app.use(express.json());

app.post('/vocals-callback', (req, res) => {
  const { code, msg, data } = req.body;
  
  console.log('Received vocal generation callback:', {
    taskId: data.task_id,
    callbackType: data.callbackType,
    status: code,
    message: msg
  });
  
  if (code === 200) {
    // Task successful
    const { callbackType, data: vocalsData } = data;
    
    switch (callbackType) {
      case 'text':
        console.log('Text generation completed');
        break;
        
      case 'first':
        console.log('First vocal track generated');
        if (vocalsData.length > 0) {
          console.log(`Track title: ${vocalsData[0].title}`);
          console.log(`Vocal audio link: ${vocalsData[0].audio_url}`);
          console.log(`Duration: ${vocalsData[0].duration} seconds`);
          console.log(`Vocals prompt: ${vocalsData[0].prompt}`);
        }
        break;
        
      case 'complete':
        console.log('All vocal tracks generated');
        console.log(`Total ${vocalsData.length} vocal tracks generated:`);
        vocalsData.forEach((track, index) => {
          console.log(`Track ${index + 1}: ${track.title} - ${track.audio_url}`);
          console.log(`Vocals: ${track.prompt}`);
        });
        
        // Process generated vocal tracks
        // Can download audio, save locally, etc.
        break;
    }
    
  } else {
    // Task failed
    console.log('Vocal generation failed:', msg);
    
    // Handle failure cases...
    if (code === 400) {
      console.log('Parameter error or vocal content violation');
    } else if (code === 429) {
      console.log('Insufficient credits');
    } else if (code === 500) {
      console.log('Server internal error');
    }
  }
  
  // Return 200 status code to confirm callback received
  res.status(200).json({ status: 'received' });
});

app.listen(3000, () => {
  console.log('Vocal callback server running on port 3000');
});

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Best Practices

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Vocal Generation Callback Configuration Recommendations

  1. Use HTTPS: Ensure your callback URL uses HTTPS protocol for secure data transmission
  2. Verify Source: Verify the legitimacy of the request source in callback processing
  3. Idempotent Processing: Ensure processing logic is idempotent as the same taskId may receive multiple callbacks
  4. Quick Response: Callback processing should return 200 status code quickly to avoid timeout
  5. Asynchronous Processing: Complex business logic should be processed asynchronously to avoid blocking callback response
  6. Stage-based Processing: Handle different callback stages (text, first, complete) with appropriate business logic
  7. Vocal Content Analysis: Implement vocal content analysis and quality assessment for generated tracks
  8. Lyrics Extraction: Extract and process lyrics from vocal prompts for better content management

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Important Reminders

  • Callback URL must be publicly accessible
  • Server must respond within 15 seconds, otherwise considered timeout
  • After 3 consecutive retry failures, the system will stop sending callbacks
  • Ensure stability of callback processing logic to avoid callback failures due to exceptions
  • Generated vocal audio URLs may have time limits, recommend downloading and saving promptly
  • Pay attention to vocal content compliance to avoid generation failures due to violations
  • Vocal generation has three stages, each stage will trigger callback notifications
  • Consider implementing content filtering for vocal lyrics and audio content

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Troubleshooting

If you don’t receive callback notifications, please check the following:

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Alternative Solutions

If you cannot use the callback mechanism, you can also use polling:

Poll Query Results

Use the Get Music Generation Details interface to regularly query task status. Recommend querying every 30 seconds.