Stretch tunings are common on pianos: instruments with plucked or hammered strings show slightly inharmonic overtones. Harmonic Tuner allows to widen octaves by 0 to 5 cent accordingly. Use the Inharmonicity protocol module to check the inharmonicity range of your strings, than set the stretch tuning accordingly.
Historical keyboard music on organs, harpsichords etc. is typically performed using historic temperaments that provide individual consonance/dissonance characteristics for each key/scale. Harmonic Tuner Intonation Expert supports a set of popular historic temperaments you can tune your instrument to. The root note of each temperament scale can be transposed. The amount of the temperament can be scaled from 5% to 100%
Youtube Demo Clip (Example: measure tuning/inharmonicity protocols of historically tempered and and stretch tuned keyboards, adjust tuner accordingly)
Youtube Demo Clip (Example: measure and compare different piano simulations on a digital piano regarding tuning and stretch, work with protocol overlays)
Setting up the tuning reference (example: unequal stretch tuning at baroque concert pitch of 415 Hz):
Protocolled sequence of tuning measurements and detected Kirnberger III temperament:
Quick-select of tuner temperament via menu: