--- title: ACE-Step v1.5 XL Base | Runware Docs url: https://runware.ai/docs/models/ace-step-v1-5-xl-base description: 4B music generation model with higher audio quality and full editing task support --- # ACE-Step v1.5 XL Base ACE-Step v1.5 XL Base is the 4B DiT variant of ACE-Step 1.5 for high-quality music generation and editing. It supports text-to-music, cover generation, repaint, extract, lego, and complete workflows, uses 50 inference steps with CFG, and is designed for longer-form audio generation up to 10 minutes with broad multilingual prompt support. - **ID**: `runware:ace-step@v1.5-xl-base` - **Status**: coming-soon - **Release Date**: April 2, 2026 - **Capabilities**: Text to Audio ## Compatibility & Validation When `inputs.audio` is provided, `duration` cannot be used. --- When `negativePrompt` is provided, `CFGScale` must be greater than `1`. --- When `settings.coverConditioningScale` is provided, `inputs.audio` is required. --- When `settings.repaintingStart` or `settings.repaintingEnd` is provided, `inputs.audio` is required. --- When `strength` is provided, `inputs.audio` is required. ## Request Parameters **API Options** Platform-level options for task execution and delivery. ### [taskType](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-tasktype) - **Type**: `string` - **Required**: true - **Value**: `audioInference` Identifier for the type of task being performed ### [taskUUID](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-taskuuid) - **Type**: `string` - **Required**: true - **Format**: `UUID v4` UUID v4 identifier for tracking tasks and matching async responses. Must be unique per task. ### [outputType](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-outputtype) - **Type**: `string` - **Default**: `URL` Audio output type. **Allowed values**: `URL` `base64Data` `dataURI` ### [outputFormat](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-outputformat) - **Type**: `string` - **Default**: `MP3` Specifies the file format of the generated output. The available values depend on the task type and the specific model's capabilities. - \`MP3\`: Compressed audio, smaller file size. - \`WAV\`: Uncompressed, high-quality audio. - \`FLAC\`: Lossless compression. - \`OGG\`: Open-source compressed audio format (Vorbis codec). **Allowed values**: `MP3` `WAV` `FLAC` `OGG` ### [audioSettings](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-audiosettings) - **Path**: `audioSettings.bitrate` - **Type**: `object (3 properties)` Audio encoding settings for controlling the bitrate, number of channels, and sample rate of the generated audio. Only applicable for lossy output formats (`MP3` and `OGG`). When using lossless formats (`WAV` or `FLAC`), this parameter must not be provided. The available sample rates and valid bitrate ranges depend on the output format. For `OGG`, bitrate limits also vary by the number of channels. **MP3 bitrate limits**: Bitrate limits for MP3 are the same regardless of mono or stereo. | Sample Rate | Min Bitrate | Max Bitrate | | --- | --- | --- | | 8,000 Hz | 8 kbps | 64 kbps | | 11,025 Hz | 8 kbps | 64 kbps | | 12,000 Hz | 8 kbps | 64 kbps | | 16,000 Hz | 8 kbps | 160 kbps | | 22,050 Hz | 8 kbps | 160 kbps | | 24,000 Hz | 8 kbps | 160 kbps | | 32,000 Hz | 32 kbps | 320 kbps | | 44,100 Hz | 32 kbps | 320 kbps | | 48,000 Hz | 32 kbps | 320 kbps | **OGG bitrate limits — Mono (1 channel)**: | Sample Rate | Min Bitrate | Max Bitrate | | --- | --- | --- | | 8,000 Hz | 8 kbps | 40 kbps | | 12,000 Hz | 16 kbps | 48 kbps | | 16,000 Hz | 16 kbps | 96 kbps | | 24,000 Hz | 16 kbps | 80 kbps | | 48,000 Hz | 32 kbps | 224 kbps | **OGG bitrate limits — Stereo (2 channels)**: | Sample Rate | Min Bitrate | Max Bitrate | | --- | --- | --- | | 8,000 Hz | 16 kbps | 80 kbps | | 12,000 Hz | 16 kbps | 96 kbps | | 16,000 Hz | 24 kbps | 192 kbps | | 24,000 Hz | 32 kbps | 160 kbps | | 48,000 Hz | 48 kbps | 256 kbps | > [!NOTE] > **Lossless formats**: When `outputFormat` is set to `WAV` or `FLAC`, the `audioSettings` parameter is not available since these formats produce uncompressed or lossless audio with no configurable encoding settings. #### [bitrate](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-audiosettings-bitrate) - **Path**: `audioSettings.bitrate` - **Type**: `integer` - **Min**: `8` Audio bitrate in kbps. #### [channels](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-audiosettings-channels) - **Path**: `audioSettings.channels` - **Type**: `integer` - **Default**: `2` Number of audio channels. 1 for mono, 2 for stereo. **Allowed values**: `1` `2` #### [sampleRate](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-audiosettings-samplerate) - **Path**: `audioSettings.sampleRate` - **Type**: `integer` Audio sample rate in Hz. ### [webhookURL](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-webhookurl) - **Type**: `string` - **Format**: `URI` Specifies a webhook URL where JSON responses will be sent via HTTP POST when generation tasks complete. For batch requests with multiple results, each completed item triggers a separate webhook call as it becomes available. **Learn more** (1 resource): - [Webhooks](https://runware.ai/docs/platform/webhooks) (platform) ### [deliveryMethod](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-deliverymethod) - **Type**: `string` - **Default**: `sync` Determines how the API delivers task results. **Allowed values**: - `sync` Returns complete results directly in the API response. - `async` Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse. **Learn more** (1 resource): - [Task Polling](https://runware.ai/docs/platform/task-polling) (platform) ### [uploadEndpoint](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-uploadendpoint) - **Type**: `string` - **Format**: `URI` Specifies a URL where the generated content will be automatically uploaded using the HTTP PUT method. The raw binary data of the media file is sent directly as the request body. For secure uploads to cloud storage, use presigned URLs that include temporary authentication credentials. **Common use cases:** - **Cloud storage**: Upload directly to S3 buckets, Google Cloud Storage, or Azure Blob Storage using presigned URLs. - **CDN integration**: Upload to content delivery networks for immediate distribution. ```text // S3 presigned URL for secure upload https://your-bucket.s3.amazonaws.com/generated/content.mp4?X-Amz-Signature=abc123&X-Amz-Expires=3600 // Google Cloud Storage presigned URL https://storage.googleapis.com/your-bucket/content.jpg?X-Goog-Signature=xyz789 // Custom storage endpoint https://storage.example.com/uploads/generated-image.jpg ``` The content data will be sent as the request body to the specified URL when generation is complete. ### [ttl](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-ttl) - **Type**: `integer` - **Min**: `60` Time-to-live (TTL) in seconds for generated content. Only applies when `outputType` is `URL`. ### [includeCost](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-includecost) - **Type**: `boolean` - **Default**: `false` Include task cost in the response. ### [numberResults](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-numberresults) - **Type**: `integer` - **Min**: `1` - **Max**: `4` - **Default**: `1` Number of results to generate. Each result uses a different seed, producing variations of the same parameters. **Inputs** Input resources for the task (images, audio, etc). These must be nested inside the \`inputs\` object. ### [audio](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-inputs-audio) - **Path**: `inputs.audio` - **Type**: `string` Audio input (UUID or URL). **Core Parameters** Primary parameters that define the task output. ### [model](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-model) - **Type**: `string` - **Required**: true - **Value**: `runware:ace-step@v1.5-xl-base` Identifier of the model to use for generation. ### [positivePrompt](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-positiveprompt) - **Type**: `string` - **Required**: true - **Min**: `2` - **Max**: `3000` Text prompt describing elements to include in the generated output. ### [negativePrompt](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-negativeprompt) - **Type**: `string` - **Min**: `2` - **Max**: `3000` Prompt to guide what to exclude from generation. Ignored when guidance is disabled (CFGScale ≤ 1). ### [duration](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-duration) - **Type**: `float` - **Min**: `30` - **Max**: `300` - **Step**: `0.1` - **Default**: `60` Length of the generated audio track in seconds. ### [seed](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-seed) - **Type**: `integer` - **Min**: `0` - **Max**: `2147483647` Random seed for reproducible generation. When not provided, a random seed is generated in the unsigned 32-bit range. ### [steps](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-steps) - **Type**: `integer` - **Min**: `1` - **Max**: `300` - **Default**: `100` Total number of denoising steps. Higher values generally produce more detailed results but take longer. ### [CFGScale](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-cfgscale) - **Type**: `float` - **Min**: `1` - **Max**: `30` - **Step**: `0.01` - **Default**: `10` Guidance scale representing how closely the output will resemble the prompt. Higher values produce results more aligned with the prompt. ### [strength](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-strength) - **Type**: `float` - **Min**: `0` - **Max**: `1` - **Step**: `0.01` - **Default**: `0.5` Fraction of steps using the input source instead of generated output. **Settings** Technical parameters to fine-tune the inference process. These must be nested inside the \`settings\` object. ### [bpm](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-bpm) - **Path**: `settings.bpm` - **Type**: `integer` - **Min**: `30` - **Max**: `300` Beats per minute. If not set, the model decides automatically. ### [cfgIntervalEnd](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-cfgintervalend) - **Path**: `settings.cfgIntervalEnd` - **Type**: `float` - **Min**: `0` - **Max**: `1` - **Step**: `0.01` - **Default**: `1` Diffusion ratio where CFG ends (1.0 = last step). ### [cfgIntervalStart](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-cfgintervalstart) - **Path**: `settings.cfgIntervalStart` - **Type**: `float` - **Min**: `0` - **Max**: `1` - **Step**: `0.01` - **Default**: `0` Diffusion ratio where CFG begins (0.0 = first step). ### [coverConditioningScale](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-coverconditioningscale) - **Path**: `settings.coverConditioningScale` - **Type**: `float` - **Min**: `0` - **Max**: `1` - **Step**: `0.01` - **Default**: `1` Fraction of denoising steps using source-audio conditioning. Only effective when input audio is provided. 1.0 uses source conditioning for all steps. ### [guidanceType](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-guidancetype) - **Path**: `settings.guidanceType` - **Type**: `string` - **Default**: `apg` Controls how guidance is applied during generation. **Allowed values**: - `apg` Adaptive Projected Guidance. - `cfg` Classifier-Free Guidance. ### [keyScale](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-keyscale) - **Path**: `settings.keyScale` - **Type**: `string` Musical key and scale in '{Note}{Accidental} {Mode}' format (e.g. 'C major', 'F# minor', 'Bb major'). ### [lyrics](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-lyrics) - **Path**: `settings.lyrics` - **Type**: `string` - **Min**: `10` - **Max**: `3000` Song lyrics, typically formatted like a lyrics website. ### [repaintingEnd](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-repaintingend) - **Path**: `settings.repaintingEnd` - **Type**: `float` - **Min**: `0` - **Max**: `300` End time in seconds for repaint region. Requires input audio. Values beyond audio duration append new audio. ### [repaintingStart](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-repaintingstart) - **Path**: `settings.repaintingStart` - **Type**: `float` - **Min**: `-300` - **Max**: `300` Start time in seconds for repaint region. Requires input audio. Negative values prepend audio before the start. ### [timeSignature](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-timesignature) - **Path**: `settings.timeSignature` - **Type**: `integer` Beats per measure. If not set, the model decides automatically. **Allowed values**: `2` `3` `4` `6` ### [vocalLanguage](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-settings-vocallanguage) - **Path**: `settings.vocalLanguage` - **Type**: `string` - **Default**: `en` ISO 639-1 language code for vocals. `unknown` for instrumental or auto detection. **Allowed values**: `unknown` `ar` `az` `bg` `bn` `ca` `cs` `da` `de` `el` `en` `es` `fa` `fi` `fr` `he` `hi` `hr` `ht` `hu` `id` `is` `it` `ja` `ko` `la` `lt` `ms` `ne` `nl` `no` `pa` `pl` `pt` `ro` `ru` `sa` `sk` `sr` `sv` `sw` `ta` `te` `th` `tl` `tr` `uk` `ur` `vi` `yue` `zh` **Features** Standalone addons and post-processing features. ### [modularScheduler](https://runware.ai/docs/models/ace-step-v1-5-xl-base#request-advancedfeatures-modularscheduler) - **Path**: `advancedFeatures.modularScheduler` - **Type**: `object` Manual scheduler configuration for fine-grained control over the diffusion process (sampler, modifiers, etc.). ## Response Parameters ### [taskType](https://runware.ai/docs/models/ace-step-v1-5-xl-base#response-tasktype) - **Type**: `string` - **Required**: true - **Value**: `audioInference` Type of the task. ### [taskUUID](https://runware.ai/docs/models/ace-step-v1-5-xl-base#response-taskuuid) - **Type**: `string` - **Required**: true - **Format**: `UUID v4` UUID of the task. ### [audioUUID](https://runware.ai/docs/models/ace-step-v1-5-xl-base#response-audiouuid) - **Type**: `string` - **Required**: true - **Format**: `UUID v4` UUID of the output audio. ### [audioURL](https://runware.ai/docs/models/ace-step-v1-5-xl-base#response-audiourl) - **Type**: `string` - **Format**: `URI` URL of the output audio. ### [audioBase64Data](https://runware.ai/docs/models/ace-step-v1-5-xl-base#response-audiobase64data) - **Type**: `string` Base64-encoded audio data. ### [audioDataURI](https://runware.ai/docs/models/ace-step-v1-5-xl-base#response-audiodatauri) - **Type**: `string` - **Format**: `URI` Data URI of the output audio. ### [seed](https://runware.ai/docs/models/ace-step-v1-5-xl-base#response-seed) - **Type**: `integer` The seed used for generation. If none was provided, shows the randomly generated seed. ### [cost](https://runware.ai/docs/models/ace-step-v1-5-xl-base#response-cost) - **Type**: `float` Task cost in USD. Present when `includeCost` is set to `true` in the request.