# Fade effect between concatenated audio tracks

When stringing a series of audio clips together using [🤖/audio/concat](/docs/robots/audio-concat.md)without using audio files at appropriate positions, it can be common to have tracks that don't mesh together very well, creating some jarring results. To reduce the odds of producing an undesirable result, we've released the `audio_fade_seconds` parameter, which adds a fade-in and out effect between each of your concatenated audio tracks.

Step 1

### Handle uploads

We can handle uploads of your users directly. [Learn more ›](/services/handling-uploads.md)

[dutch-anthem.mp3](https://demos.transloadit.com/16/b05526376f4bcb896006d44825b5fd/dutch-anthem.mp3)

Audio · 911 KB · 58s

```
":original": {
  "robot": "/upload/handle"
}
```

🤖 [/upload/handle](/docs/robots/upload-handle.md)

This bot receives uploads that your users throw at you from browser or apps, or that you throw at us programmatically

Step 2

### Import files from web servers

We are happy to import from whatever storage solution suits you best. [Learn more ›](/services/file-importing.md)

[german-anthem.mp3](https://demos.transloadit.com/a4/dcdafab085485986f8499bab6148b3/german-anthem.mp3)

Audio · 1.2 MB · 78s

```
"imported": {
  "robot": "/http/import",
  "url": "https://demos.transloadit.com/inputs/german-anthem.mp3"
}
```

🤖 [/http/import](/docs/robots/http-import.md)

This bot imports any file that is publicly available via a web URL into Transloadit

Step 3

### Concatenate audio

We offer a variety of features to reduce audio size while maintaining quality, as well as add effects like loops or watermarks. [Learn more ›](/services/audio-encoding.md)

[dutch-anthem\_german-anthem.mp3](https://demos.transloadit.com/ef/63949355654c3bad73a645dbb82a35/dutch-anthem%5Fgerman-anthem.mp3)

Audio · 2.1 MB · 136s

```
"concatenated": {
  "use": {
    "steps": [
      {
        "name": ":original",
        "as": "audio_1"
      },
      {
        "name": "imported",
        "as": "audio_2"
      }
    ]
  },
  "robot": "/audio/concat",
  "result": true,
  "audio_fade_seconds": 1,
  "ffmpeg_stack": "v7"
}
```

🤖 [/audio/concat](/docs/robots/audio-concat.md)

This bot concatenates several audio files together

Step 4

### Export files to Amazon S3

We export to the storage platform of your choice. [Learn more ›](/services/file-exporting.md)

`:original`

* [https://demos.transloadit.com/16/b05526376f4bcb896006d44825b5fd/dutch-anthem.mp3⁠](https://demos.transloadit.com/16/b05526376f4bcb896006d44825b5fd/dutch-anthem.mp3)

`imported`

* [https://demos.transloadit.com/a4/dcdafab085485986f8499bab6148b3/german-anthem.mp3⁠](https://demos.transloadit.com/a4/dcdafab085485986f8499bab6148b3/german-anthem.mp3)

`concatenated`

* [https://demos.transloadit.com/ef/63949355654c3bad73a645dbb82a35/dutch-anthem\_german-anthem.mp3⁠](https://demos.transloadit.com/ef/63949355654c3bad73a645dbb82a35/dutch-anthem%5Fgerman-anthem.mp3)

```
"exported": {
  "use": [
    "concatenated",
    "imported",
    ":original"
  ],
  "robot": "/s3/store",
  "credentials": "demo_s3_credentials",
  "url_prefix": "https://demos.transloadit.com/"
}
```

🤖 [/s3/store](/docs/robots/s3-store.md)

This bot exports encoding results to Amazon S3

## Live Demo. See for yourself

Loading Uppy demo…

This live demo is powered by [Uppy⁠](https://uppy.io/docs/guides/uppy-transloadit/), our open source file uploader that you can also use without Transloadit, and [tus⁠](https://tus.io), our open protocol for resumable file uploads that is making uploading more reliable across the world.

## Build this in your own language

```
<!-- This pulls Uppy from our CDN -->
<!-- For smaller self-hosted bundles, install Uppy and plugins manually: -->
<!-- npm i --save @uppy/core @uppy/dashboard @uppy/remote-sources @uppy/transloadit ... -->
<link
  href="https://releases.transloadit.com/uppy/v3.10.0/uppy.min.css"
  rel="stylesheet"
/>
<button id="browse">Select Files</button>
<script type="module">
  import {
    Uppy,
    Dashboard,
    ImageEditor,
    RemoteSources,
    Transloadit,
  } from 'https://releases.transloadit.com/uppy/v3.10.0/uppy.min.mjs'
  const uppy = new Uppy()
    .use(Transloadit, {
      waitForEncoding: true,
      alwaysRunAssembly: true,
      assemblyOptions: {
        params: {
          // It's often better store encoding instructions in your account
          // and use a `template_id` instead of adding these steps inline
          steps: {
            ':original': {
              robot: '/upload/handle',
            },
            imported: {
              robot: '/http/import',
              url: 'https://demos.transloadit.com/inputs/german-anthem.mp3',
            },
            concatenated: {
              use: {
                steps: [
                  {
                    name: ':original',
                    as: 'audio_1',
                  }, 
,                  {
                    name: 'imported',
                    as: 'audio_2',
                  }, 
                ],
              },
              robot: '/audio/concat',
              result: true,
              audio_fade_seconds: 1,
              ffmpeg_stack: 'v7',
            },
            exported: {
              use: ['concatenated', 'imported', ':original'],
              robot: '/s3/store',
              credentials: 'demo_s3_credentials',
              url_prefix: 'https://demos.transloadit.com/',
            },
          },
        },
      },
    })
    .use(Dashboard, { trigger: '#browse' })
    .use(ImageEditor, { target: Dashboard })
    .use(RemoteSources, {
      companionUrl: 'https://api2.transloadit.com/companion',
    })
    .on('complete', ({ transloadit }) => {
      // Due to `waitForEncoding:true` this is fired after encoding is done.
      // Alternatively, set `waitForEncoding` to `false` and provide a `notify_url`
      console.log(transloadit) // Array of Assembly Statuses
      for (const assembly of transloadit) {
        console.log(assembly.results) // Array of all encoding results
      }
    })
    .on('error', (error) => {
      console.error(error)
    })
</script>

```

[Read docs: Browsers](/docs/sdks/uppy.md)

## So many ways to integrate

Transloadit is a service for companies with developers. And there are many ways developers can put Transloadit to good use inside your company to automate media processing.

#### Bulk imports

Add one of our [import Robots](/services/file-importing.md) to acquire and transcode massive media libraries.

#### Handling uploads

We are *the* experts at reliably [handling uploads](/services/handling-uploads.md). We wrote the [protocol⁠](https://tus.io/) for it.

#### Front-end integration

We integrate with web browsers via our next-gen file uploader [Uppy⁠](https://uppy.io/docs/guides/uppy-transloadit/) and SDKs for Android and iOS.

#### Back-end integration

Send us batch jobs in any server language using one of our [SDKs](/docs/sdks.md) or directly interfacing with our [REST API](/docs/api.md).

#### Pingbacks

Configure a [notify\_url](/services/content-delivery.md) to let your server receive transcoding results JSON in the `transloadit` POST field.

#### On-demand

Use our [Smart CDN](/services/file-importing.md) to adapt files on-demand and stream them directly to your users.

[Browsers](/docs/sdks/uppy.md)[TransloaditKit](/docs/sdks/transloaditkit.md)[Ruby SDK](/docs/sdks/ruby-sdk.md)[HTTP REST API](/docs/api.md)[Python SDK](/docs/sdks/python-sdk.md)[PHP SDK](/docs/sdks/php-sdk.md)[Node.js SDK](/docs/sdks/node-sdk.md)[Java SDK](/docs/sdks/java-sdk.md)[Go SDK](/docs/sdks/go-sdk.md)[cURL](/docs/sdks/curl.md)[Convex](/docs/sdks/convex.md)

[Browsers](/docs/sdks/uppy.md)[TransloaditKit](/docs/sdks/transloaditkit.md)[Ruby SDK](/docs/sdks/ruby-sdk.md)[HTTP REST API](/docs/api.md)[Python SDK](/docs/sdks/python-sdk.md)[PHP SDK](/docs/sdks/php-sdk.md)[Node.js SDK](/docs/sdks/node-sdk.md)[Java SDK](/docs/sdks/java-sdk.md)[Go SDK](/docs/sdks/go-sdk.md)[cURL](/docs/sdks/curl.md)[Convex](/docs/sdks/convex.md)

[Browsers](/docs/sdks/uppy.md)[TransloaditKit](/docs/sdks/transloaditkit.md)[Ruby SDK](/docs/sdks/ruby-sdk.md)[HTTP REST API](/docs/api.md)[Python SDK](/docs/sdks/python-sdk.md)[PHP SDK](/docs/sdks/php-sdk.md)[Node.js SDK](/docs/sdks/node-sdk.md)[Java SDK](/docs/sdks/java-sdk.md)[Go SDK](/docs/sdks/go-sdk.md)[cURL](/docs/sdks/curl.md)[Convex](/docs/sdks/convex.md)

## Other cool demos

* [View demo→Audio EncodingAdd echo to an audio file](/demos/audio-encoding/ffmpeg-add-echo.md)
* [View demo→Audio EncodingAdd watermark to a song](/demos/audio-encoding/implement-audio-watermarking.md)
* [View demo→Document ProcessingAdd a header or footer to a PDF](/demos/document-processing/add-header-or-footer-to-pdf.md)

Try Transloadit

## Ready to get started?

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