Now let me read the existing files to understand the project structure before building:

Now let me build this chord-to-MIDI tool. I'll create a dark-themed music tool with a professional UI. Let me start with the theme, then build the components.

Now let me add the midi-writer-js and tone packages, and build all the components:

Now let me update the layout with proper metadata:

Now update the font references in globals.css:

Now let me create the core MIDI utilities:

Now let me create the MIDI generator utility:

Now let me create the piano keyboard visualization component:

Now let me create the chord tag/chip component:

Now let me create the playback controls component:

Now let me create the settings panel:

Now let me create the chord reference panel:

Now let me create the main chord editor component that brings everything together:

Now let me create the main page:

Let me check if the slider component exists and verify it's set up correctly:

All UI components are available. Let me also verify the midi-writer-js types are handled correctly by checking how the module is imported:

The latest version is 3.1.1. Let me update the package version and ensure the import works properly:

Now let me update the midi-generator to use the correct v3 API where Writer takes an array:

The code looks good. Now let me also make sure the Pitch types work correctly. In v3, the types might have changed. Let me update the import to be safer with types:

Now let me verify the Tone.js import approach in the chord editor is correct - Tone.js can be tricky with SSR. Let me also check that the Tone type import is working:

I need to fix the Tone.js import pattern - tone v15 uses a different module structure. Let me update the import:

The app should now be building. Let me verify everything looks correct by checking the final state of the key files:

The app is complete. Here's a summary of what I built:

ChordMIDI - 和弦音名转 MIDI 工具，一个完全在浏览器端运行的离线工具，包含以下功能：

1. 和弦解析引擎 (lib/midi-utils.ts) - 支持解析 30+ 种和弦类型（大三、小三、七、九、增、减、挂留、转位和弦等），将和弦名称转换为 MIDI 音符编号
2. MIDI 生成器 (lib/midi-generator.ts) - 使用 midi-writer-js 将和弦序列生成标准 MIDI 文件，支持自定义 BPM、音符时值和力度
3. 在线播放预览 - 通过 Tone.js 合成器实时播放和弦序列，支持逐个和弦试听、顺序播放、上一个/下一个导航
4. 可视化钢琴键盘 - 动态高亮当前播放和弦的音符位置，带有发光效果
5. 一键导出 MIDI 文件 - 直接下载 .mid 文件，可导入任何 DAW 软件使用

界面采用深色音乐工具主题，支持快速输入面板、参数设置（BPM/时值/力度/八度），以及 Ctrl+Space 快捷键控制播放。

Now let me also read the piano keyboard and page to understand the full picture:

Now I have a full picture of the codebase. I need to:

1. Add timbre (音色) selection - different Tone.js synth oscillator types
2. Add volume control - Tone.js master volume
3. Add theme switching - multiple color themes stored in CSS + a theme provider

Let me create the theme provider first, then update the settings panel and chord editor.

Good, there's already a theme-provider file. Let me replace it with a custom multi-theme provider, then update the settings panel and chord editor.

Now create the theme switcher component:

Now update the settings panel to include timbre and volume controls:

Now update the chord editor to add timbre, volume, theme states, rebuild the synth when timbre changes, and integrate the theme switcher:

Now add timbre and volume state variables:

Now replace the synth creation logic to use timbre and volume:

Now add the theme toggle button in the header and the theme panel in the UI:

Now add the theme panel section right after the header, before the chord reference:

Now update the SettingsPanel usage to pass timbre and volume:

Now wrap the page with the ThemeProvider:

Now let me also clean up the unused Palette import from chord-editor since it's actually used in the new button — let me verify:

Good, Palette is used. Let me also ensure the page.tsx is using 'use client' since it wraps with ThemeProvider which requires a client boundary — but actually ThemeProvider itself is 'use client', and it's imported into a server component which is fine. Let me verify the page still works as RSC since ThemeProvider is a client component imported into it:

This is fine -- ThemeProvider and ChordEditor are both 'use client' components, so importing them into the RSC page is correct (Next.js will render them as client components on the boundary).

Let me do one final verification to make sure the full chord editor file is coherent:

Everything looks correct. Here's a summary of the changes:

新增三个功能：

1. 预览音色选择 -- 在参数设置中新增了 6 种音色选项（三角波、正弦波、方波、锯齿波、厚正弦、厚三角），切换音色时会自动重建 Tone.js 合成器实例，使用对应的振荡器波形。
2. 预览音量控制 -- 新增 0-100% 音量滑块，通过 Tone.js 的 Volume 节点实现分贝级精确控制，调整音量时无需重建合成器，实时生效。
3. 主题切换 -- 提供 5 套配色主题（午夜/海洋/日落/森林/玫瑰），点击顶部调色板图标展开主题面板，选择后即时切换所有 CSS 变量，主题偏好通过 localStorage 持久化。