Feature Request: add 'also export in concert pitch' option

[opinsky]

The option to export both in transposed pitch and in concert pitch would be a great addition to the plugin.

The use case is music that will be read by musicians in both transposing and non-transposing instruments. Batch_export could generate PDFs or EPUBs for both formats.

As a potential road-map feature, the ability to transpose into other tunings before exporting would be an even better feature. For example: PDFs of music exported in non-transposing (e.g flute), Bb transposing (e.g clarinet) and Eb transposing (e.g. Alto Sax) instruments.

[lgvr123]

Hi, I just rebased my previous code, and Jojo merged it into its master. So feel free to start this change. I saw there is a concertPitch but I don't know to which element it is attached and how it works.