Transposer (Chinese display name: 键盘移调器; “the App”) is a visual iOS tool that lets you control compatible electronic keyboards and reach transpose settings in one tap. The App is a MIDI transpose utility for iOS—no account is required, and it does not connect to our backend services.
You can connect a compatible keyboard over USB or Bluetooth MIDI.
USB
Bluetooth MIDI
The App uses CoreMIDI over USB and Bluetooth MIDI (BLE MIDI) to communicate with compatible musical instruments. Bluetooth MIDI keyboards do not appear in iOS Settings > Bluetooth; connect them from inside the App, not from system Bluetooth settings. Bluetooth page-turn pedals (for example AirTurn or PageFlip) are different: pair those in iOS Settings, then use them while a score is open.
The App may store the following locally on your device only:
This data never leaves your device unless you export or share it.
The App may keep an audio session active so USB or Bluetooth MIDI can continue while the screen is locked or the App is in the background. The App does not access the microphone, record audio, or upload audio data.
What should I do if my iOS device doesn’t recognize a Type-B-to-USB connection through a Type-C hub?
Use a MIDI-to-USB cable instead. Some older keyboards do not support OTG connections; connecting with a MIDI-to-USB cable should allow the App to work.
Why doesn’t my Bluetooth MIDI keyboard appear in iOS Settings > Bluetooth?
That is expected. BLE MIDI keyboards are not listed like headphones. Open Devices in the App, tap Bluetooth MIDI, and connect there. After Connect is on, the keyboard appears under Available MIDI Devices.
What should I do if my device model isn’t in the supported manufacturer list?
The App supports essentially all keyboard models commonly used for live performance. If your model isn’t listed, first check whether your instrument can turn off Local Control. If it can, disable Local Control, select Unknown Model in the App, and try whether transpose control works.
Do I need to create an account?
No. The App works without registration.
Does the App collect my personal data?
No. We do not collect, store on our servers, sell, or share your personal information. See our Privacy Policy for details.
For support questions, contact: 1284643046@qq.com
Transposer Terms of Use (EULA)
键盘移调器（英文名 Transposer；「本应用」）是一款可视化 iOS 设备控制电子键盘乐器、一键直达移调的工具。本应用为 iOS MIDI 移调工具，无需注册账号，也不连接我们的后端服务。
可通过 USB 或蓝牙 MIDI 连接兼容键盘。
USB
蓝牙 MIDI
本应用通过 USB MIDI 和蓝牙 MIDI（BLE MIDI）使用 CoreMIDI 与兼容的电子乐器通信。蓝牙 MIDI 键盘不会出现在 iOS「设置 → 蓝牙」里，请在应用内连接，不要在系统蓝牙设置中搜索。蓝牙翻谱踏板（例如 AirTurn、PageFlip）是另一类设备：请先在 iOS 设置中配对，打开谱面后即可翻页。
本应用可能仅在您的设备上本地保存：
除非您主动导出或分享，否则上述数据不会离开您的设备。
本应用可能保持音频会话处于活动状态，以便在锁屏或进入后台时继续维持 USB 或蓝牙 MIDI。应用不会访问麦克风、不会录音，也不会上传音频数据。
如果用 Type-B 转 USB 连接到 iOS 设备的 Type-C 扩展坞，iOS 设备不识别怎么办？
请使用 MIDI 转 USB 的线进行连接。由于一些稍早的设备不支持 OTG 连接，需要用 MIDI 转 USB 的线进行连接即可使用。
为什么蓝牙 MIDI 键盘在 iOS「设置 → 蓝牙」里搜不到？
这是正常现象。BLE MIDI 键盘不会像耳机那样出现在系统蓝牙列表中。请在应用的「设备」页点「蓝牙 MIDI」进行连接；打开 Connect 后，键盘会出现在「可用 MIDI 设备」里。
我的设备型号不在支持的厂家设备型号列表里面怎么办？
本 App 基本上支持了市面上所有的演出在用的型号。如果不在支持的列表中，先确认自己的设备是否可以关闭 Local Control；如果可以的话，请关闭 Local Control 并在 App 内选择「未知型号」，尝试一下是否可以进行移调控制。
需要注册账号吗？
不需要。本应用无需注册即可使用。
应用会收集我的个人信息吗？
不会。我们不会收集、不会在服务器上存储、不会出售或分享您的个人信息。详情请参阅隐私政策。
如有使用或技术支持相关问题，请联系：1284643046@qq.com