Alpine accentor – Prunella collaris
The Alpine accentor, along with the Altai accentor is sometimes separated from the other accentors, into the genus Laiscopus.

The word “accentor” is from post-classical Latin and means a person who sings with another. The genus name Prunella is from the German Braunelle, “dunnock”, a diminutive of braun, “brown”.

It builds a neat nest low in a bush or rock crevice, laying 3-5 unspotted sky-blue eggs.

The mating system is of particular interest. Home ranges are occupied by breeding groups of 3 or 4 males with 3 or 4 females. These are unrelated birds which have a socially polygynandrous mating system. Males have a dominance hierarchy, with the alpha males being generally older than subordinates. Females seek matings with all the males, although the alpha male may defend her against matings from lower ranking males. In turn, males seek matings with all the females. DNA fingerprinting has been used to show that, within broods, there is often mixed paternity, although the female is always the true mother of the nestlings raised within her nest. Males will provide food to chicks at several nests within the group, depending on whether they have mated with the female or not – males only provide care when they are likely to be the true fathers of the chicks.

It sounds like this
Recording by Jarek Matusiak from Xeno canto