Like the German "ich" (in the opposite direction too - chi) when χ comes before or after an ι, η, υ, etc sound (e.g. in εὐχή, χειμών, εἶχε, etc). The k sound is common when non Greeks read Greek, which means that in the audio files that you use maybe the texts are not read by Greeks. X is never pronounced as a k. For example, the Latin Christus contains two errors, first the pronunciation of X as k, and second the stress to the first syllable, instead of the last - it should be Hristos.

Ἔρρωσο!

So in Χριστος the sound is like "ich" also, as well as with Χ + ε ι η υ and combinations of these vowels? Is the Χ like "ach" elsewhere, like in χάρις or χόρτος?

Philios

In Χριστός the χ is not pronounced like an ich (there is no ι, η, υ, etc, that follows, but a ρ), it is pronounced as in χάρις or χόρτος. Note that for the ich sound the ι (or η, or υ, etc) must be immediately after or before χ.

I take it then that in Χριστος and other words with the combination χρ-, as well as words like χάρις and χόρτος the "ach" sound is used. Correct?

Ευχαριστω ωφελεια σου!

Philios

Yes. In all cases when χ is not followed or preceded by ι, υ, η, etc., its sound resembles the χ sound of "ach" or "och".