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mcp_opendaw_create_bordun

Create a sustained drone chord (bordun) for harmonic foundation. Specify root, intervals, and duration to add a textural layer using open fifths, octaves, or chord drones.

Instructions

Create a bordun — continuously sustained drone chord as a textural layer.

A bordun (bourdon) is a continuously sounding tone or chord that provides a harmonic foundation beneath changing melody. Unlike pedal_point (which is a single repeated/anchored note), the bordun is a sustained textural layer — often an open fifth, octave, or drone chord. Found in Scottish bagpipes, Indian tanpura, hurdy-gurdy, ambient drone music, and folk.

root: Root note name (e.g. "C", "Ab", "F#"). octave: Octave for the bordun (1-6, default 3 = low register). intervals: Comma-separated semitone intervals from root (e.g. "0,7" = open fifth, "0,7,12" = octave+fifth, "0,3,7" = minor triad drone, "0,5" = open fourth). bars: Total length in bars (1-16, default 4). beats_per_bar: Time signature beats (3/4=3, 4/4=4, 6/8=6, default 4). velocity: Velocity of bordun notes (0-1, default 0.55 — softer than melody). retrigger_bars: If >0, re-triggers the bordun every N bars (e.g. 2 = retrigger every 2 bars). If 0, one continuous sustained note for entire duration. unit_index: AU index with note track (-1 = find first AU with note tracks). track_index: Note track index within the AU. start_beat: Position in beats where the bordun begins.

Returns notes created, pitches, total duration.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
barsNo
rootNoC
octaveNo
velocityNo
intervalsNo0,7
start_beatNo
unit_indexNo
track_indexNo
beats_per_barNo
retrigger_barsNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries full responsibility. It details the effect (creates sustained drone chord) and parameters, but does not disclose potential side effects, mutability, or whether it overwrites existing notes. Some behavioral aspects like note creation and retriggering are covered, but safety and idempotency are missing.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is well-structured with a clear definition, musical context, and a parameter list. It is somewhat lengthy but each sentence adds value. It could be slightly more concise without losing clarity.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description covers all parameters, distinguishes from sibling tools, and mentions return values. With an output schema present, the return value description is adequate. The musical examples provide rich context, making it complete for agent use.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 0% description coverage, but the tool description provides exhaustive explanations for all 10 parameters, including defaults, ranges, and musical semantics. This fully compensates for the missing schema descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Create a bordun — continuously sustained drone chord as a textural layer.' It provides a specific verb and resource, and explicitly contrasts with the sibling tool pedal_point, making it easy to differentiate.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explains what a bordun is and where it is used, and contrasts it with pedal_point. However, it does not explicitly state when to use or not use this tool, nor does it specify alternatives beyond the one contrast.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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