Tonartwechsel für Sänger

# 1) Request a presigned URL → returns { uploadUrl, storageKey }
curl -X POST 'https://api.elysiatools.com/api/upload/presign/audio-key-change-for-singers' \
  -H 'Content-Type: application/json' \
  -d '{"filename":"audioFile.ext","contentType":"application/octet-stream","size":12345}'

# 2) PUT the file bytes directly to the presigned uploadUrl
curl -X PUT '<presigned uploadUrl>' \
  --data-binary @/path/to/file.ext

# 3) Call the tool, passing the returned storageKey for each file field
curl -X POST 'https://api.elysiatools.com/de/api/tools/audio-key-change-for-singers' \
  -F 'audioFile=uploads/2026/01/01/your-tool-1700000000000-abc123.ext' \
  -F 'changeMethod=keys' \
  -F 'sourceKey=C' \
  -F 'targetKey=D' \
  -F 'semitones=0' \
  -F 'octaveOffset=0' \
  -F 'preserveFormants=true' \
  -F 'outputFormat=wav'