Description
Transpose MIDI note-on/off and polyphonic key-pressure note fields only, rejecting out-of-range pitches rather than clipping; other records remain unchanged.
MIDI 1.0 channel messages use a status byte identifying a message type and a channel, followed by one or two seven-bit data bytes. This family uses channel indexes 0–15 and raw program values 0–127. Raw message bytes do not include musical timing, instrument state or a MIDI file container.1
Transpose MIDI note-on/off and polyphonic key-pressure note fields only, rejecting out-of-range pitches rather than clipping; other records remain unchanged.
When to use this tool
Use this tool to transpose MIDI note-on/off and polyphonic key-pressure note fields only, rejecting out-of-range pitches rather than clipping; other records remain unchanged.
How to use the tool and how it works
- Enter messagesJson, semitones using the field definitions below. For JSON text, serialize the explicit records in the shown shape.
- Run the operation. Correct input errors before interpreting an output.
- Read result.messages. Use the ordering, boundary rules and absence conditions described below.
Add semitones to the note byte in note-off, note-on and polyphonic key-pressure records. Preserve other fields and message types.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| messagesJson | JSON text encoding array of {status: number, data: array of number}. Keep the record keys and value types shown in the decoded example below. | Text, at most 8,192 UTF-16 code units; the operation’s grammar also applies. |
| semitones | Signed integer note shift, −127 through 127 semitones. | A finite safe integer within the operation’s stated bounds. |
These are the decoded structures used in the example’s JSON text fields. Supply the corresponding serialized JSON strings as input.
{
"messagesJson": [
{
"status": 144,
"data": [
60,
100
]
}
]
}| Output field | Interpretation |
|---|---|
| result | Object containing the named fields below. |
| result.messages | Explicit validated or transformed {status, data} records in source order. |
{
"input": {
"messagesJson": "[{\"status\":144,\"data\":[60,100]}]",
"semitones": 2
},
"output": {
"result": {
"messages": [
{
"status": 144,
"data": [
62,
100
]
}
]
}
}
}Limitations and assumptions
- Any transposed note outside 0–127 is an error rather than clipped or wrapped.
- Message data bytes must be integers 0–127 and channel statuses 128–239. Channels are zero-based; this family does not implement MIDI 2.0 UMP, audio synthesis or a complete timed MIDI file.
- Every declared top-level input field is required and unexpected fields are rejected. Ordinary strings are limited to 8,192 UTF-16 code units and lists to 128 entries, with tighter operation-specific bounds where stated. JSON text has bounded nesting and node counts.
- Numeric outputs must be finite and no larger in absolute magnitude than the safe-integer limit; operations returning exact large integers use decimal text. Positions are zero-based and spans end exclusively unless the operation explicitly states a different convention.
Alternative or Complementary methods
Separate channel-message encoding from timing, running status and device interpretation. Use a MIDI sequencer or full file/stream parser when those additional layers matter.
References
-
Summary of MIDI 1.0 Messages — The MIDI Association
-
Tool behavior and example: MIDI Channel Message Note Transposer — tool.io
Similar or alternative tools
- MIDI Channel Message Byte Count
Return required MIDI 1.0 channel-message byte counts from an explicit status, excluding running-status omission and system messages.
- MIDI Channel Message Channel Remapper
Remap all MIDI channel-message channels through an explicit sixteen-entry old-to-new channel table; preserve message type and data.