Split pitch_ namespaces into note_ and contour_

As discussed in #91 starting here, currently the pitch_hz and pitch_midi namespaces are overloaded in a bad way, supporting both note-style annotations (where a note has a start time, duration, and pitch) and continuous f0 (contour)-style annotations (where contours are specified by timestamped pitch values with 0 duration).

Apart from being confusing, this causes a number of problems e.g. for sonification and visualization.

The proposed solution is to split “pitch” into “note” and “contour”, keeping the hz/midi distinction as well:

1. note_hz
2. note_midi
3. contour_hz
4. contour_midi Note that the only difference between hz and midi here is how pitch values are represented (on a Hertz scale or as MIDI note numbers), but the two are otherwise equivalent: neither implies any sort of pitch quantization, and both can be used to represent sparse (note) annotations and dense (contour) annotations.

Finally, we need to decide whether to use the aforementioned namespace names as is or add a pitch_ prefix to each of the 4 (the former means shorter/cleaner namespace names, the latter is less ambiguous).

[bmcfee]

If I recall correctly the assumption was that pitch_hz would be used for time series and pitch_midi would be used for notes,

Right – I’m talking about the old (deprecated) namespaces where that was implicit, not the new note_* namespaces.

I just wanted to make sure that we’re agreed that implicit voicing does not exist in midi space. I think we’re 👍 though. Thanks for clarification!

[justinsalamon]

If I recall correctly the assumption was that pitch_hz would be used for time series and pitch_midi would be used for notes, where voicing is indicating implicitly by the absence of a note. But in practice either namespace could be used to represent both a frequency time series or a set of notes.

Long story short, yeah, I guess we didn’t support unvoiced frequencies for midi namespaces. Won’t be a problem with the new namespaces, for conversion I guess lets just say unvoiced is not supported for midi.