[Music Gen / Lyria] INTERNAL ERROR: "Rewriter Chunk does not have function call"

[twin kraken]

The music generation tool is consistently failing when prompts specify structural rhythmic patterns or isolated percussion (e.g., dry industrial beats or high-BPM syncopated loops). While standard "pop song" prompts with full instrumentation and lyrics seem to process, requests for specific, minimalist, or avant-garde structures trigger a backend dependency error in the rewriter.
Steps to Reproduce:

1. Enter a prompt for a high-tempo, isolated percussion track (e.g., "190 BPM dry, isolated kick drum with a highly syncopated, stuttering rhythm and no other instruments").
2. Submit for generation.
3. Observe immediate failure without audio output.

   Relevant Environment Details & Error Log:

• Model: Lyria 3 (via Gemini integration)
• Error Log: ```text Run tool failed: INTERNAL: Failed to run music generation (original status: INVALID_ARGUMENT): invalid status beyond::dependency::3: Rewriter Chunk does not have function call. [https://www.google.com/search?q=type.googleapis.com/util.MessageSetPayload%3D'430855239 { 1: "bard/llm/lyria_3/0.0.1-gacf" 2 { 1: 3 2: "generic" 3: "invalid status beyond::dependency::3: Rewriter Chunk does not have function call." } }']

[thick cape]

Hi there @twin kraken, thanks for flagging this! I was not able to reproduce this issue using the Gemini app. Where are you experiencing this issue exactly?

[twin kraken]

Thanks for the follow-up! I've done some deeper testing and can confirm the issue persists across multiple platforms.
The test results:

• iPhone 15 (Standard): Failed using the same prompt.
• iMac (macOS 10.15.8 / Chrome 128): Failed consistently with the Rewriter Chunk does not have function call error.

  The Exact Prompt used for reproduction: “190 BPM dry, isolated kick drum with a highly syncopated, stuttering rhythm and no other instruments.”
  Observation: It seems the error triggers specifically when the prompt bypasses standard 'song' structures (lyrics/melody) and asks for raw, structural rhythmic patterns. Even on the newest iOS hardware, the 'Rewriter' appears to be failing to translate these specific percussive requests into a valid function call for the engine.
  If you are unable to reproduce it on your end, could you let me know if you are using a specific internal build or if there are regional rollouts for the Lyria rewriter logic that might differ from the public version?

[tough galleon]

.k

[twin kraken]

I’ve spent the last hour stress-testing this across web (MacOS 10.15.8/Chrome 128) and mobile (iPhone 15) and found two distinct failure states with the Lyria rewriter/engine:

1. The "channel allocation" crash (ret_check failure): when a prompt asks for a strictly repetitive, minimalist rhythm using the same word (like "bob ... bob bob ... bob bob"), the engine fails every time with: invalid_argument: ret_check failure ... raw_samples.num_channels() > 0 (0 vs. 0).

If the prompt is too "mathematically thin" (high bpm + silence + repetitive vocals), the engine fails to allocate audio channels and crashes before it even renders.

2. The alignment logic failure: if i change the words to "trick" the engine into actually working (e.g., "bob... hob hob... gob gob"), the track generates, but it completely ignores the drum instructions.

Even when explicitly told "loud drum beat must be heard on every syllable," the engine just gives me a generic 190 bpm industrial loop that isn't synced to the vocal cadence at all.

The rewriter can handle generic genres, but it has a massive blind spot for structural rhythmic logic. It’s treating lyrics and drums as two disconnected layers instead of a single rhythmic instruction. This happens on both my phone and my desktop.

Prompt used for test: “190 bpm industrial, use only drums and keep strictly to lyrics: Bob ... Hob Hob ... Gob Gob…”