In Kazakh, the instrumental case is -Men. That “e” is really “e”, not “low vowel”. It does not observe the laws of vowel harmony (though I did capitalise the “m” because of the consonant assimilation). So the above examples could just as well read “өз құлақыңмен тыңдау” (öz qulaqıñmen tıñdaw) and “өз құлағымызбен тыңдағанбыз” (öz qulağımızben tıñdağanbız). Hopefully some of my readers already speak a little of some other Turkic variety and I’ve have just become convinced–through the sheer majesty of the sound of Kazakh speech–to get a hold of Karl A. Krippes’s “Kazakh Grammar with Affix List”, out of which that scan was taken.
Consonantal assimilation for -Men isn’t just about denasalising, but also about full-devoicing, as this propaganda displays admirably:
But if you were to look in the prescriptive grammars for other Turkic varieties, you would believe that this was a feature unique to Kazakh. After all, certain Oğuz varieties which have something resembling an instrumental only developed it by shortening the postpositional for “with”, so this is a suffix unique to Kazakh, right?
Obviously I don’t think it’s right or I wouldn’t be asking. Although it’s not mentioned in most grammars of the Istanbul standard, it is quite common in Turkey to hear what appears to be a long-lost cousin of -Men: -nAn. Unlike -Men the initial consonant doesn’t undergo any sort of assimilation, but the low vowel harmonises just as the ones in the ablative, dative and locative do: Kaşıknan, kalemnen, bıçaknan, gözlüknen, and so forth. Perfectly regular, widely used, but not an official suffix.