When you submit a task to the music extension 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 extended music track generated (first stage)
  • All extended music tracks generated (complete stage)
  • Music extension 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 - Music extension completed
400Bad Request - Invalid source audio or parameter error
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 extended music track generated
  • complete: All extended music 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
Music extension result information, returned on success
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data.data[].id
string
Audio unique identifier
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data.data[].audio_url
string
Extended audio file download link
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data.data[].source_audio_url
string
Original extended audio file download link
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data.data[].stream_audio_url
string
Streaming audio playback link
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data.data[].image_url
string
Music cover image link
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data.data[].prompt
string
Extension prompt used
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data.data[].model_name
string
AI model name used for extension
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data.data[].title
string
Extended music title
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data.data[].tags
string
Music style tags
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data.data[].createTime
string
Creation time
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data.data[].duration
number
Extended 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('/extend-callback', (req, res) => {
  const { code, msg, data } = req.body;
  
  console.log('Received music extension callback:', {
    taskId: data.task_id,
    callbackType: data.callbackType,
    status: code,
    message: msg
  });
  
  if (code === 200) {
    // Task successful
    const { callbackType, data: musicData } = data;
    
    switch (callbackType) {
      case 'text':
        console.log('Text generation completed');
        break;
        
      case 'first':
        console.log('First extended music track generated');
        if (musicData.length > 0) {
          console.log(`Extended music title: ${musicData[0].title}`);
          console.log(`Audio link: ${musicData[0].audio_url}`);
          console.log(`Duration: ${musicData[0].duration} seconds`);
        }
        break;
        
      case 'complete':
        console.log('All extended music tracks generated');
        console.log(`Total ${musicData.length} extended tracks:`);
        musicData.forEach((track, index) => {
          console.log(`Track ${index + 1}: ${track.title} - ${track.audio_url}`);
        });
        
        // Process extended music
        // Can download music, save locally, etc.
        break;
    }
    
  } else {
    // Task failed
    console.log('Music extension failed:', msg);
    
    // Handle failure cases...
    if (code === 400) {
      console.log('Invalid source audio or parameter error');
    } 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('Extension callback server running on port 3000');
});

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Best Practices

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Music Extension Callback Configuration

  1. Source Validation: Verify that the original audio source is valid before processing extension callbacks
  2. Duration Tracking: Monitor the extended duration to ensure it meets your requirements
  3. Quality Check: Implement quality checks for the extended audio segments
  4. Version Control: Keep track of extension iterations and maintain version history
  5. Fallback Handling: Implement fallback mechanisms if extension fails
  6. Seamless Integration: Ensure the extended portion integrates smoothly with the original track

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Extension-Specific Considerations

  • Extension tasks require a valid source audio file
  • The continueAt parameter determines where the extension begins
  • Extended tracks maintain the style and characteristics of the original
  • Extension quality depends on the source audio quality
  • Some complex musical structures may be challenging to extend seamlessly

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Troubleshooting

Common issues specific to music extension callbacks:

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Alternative Solutions

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

Poll Extension Results

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