The schematic picture below shows the evolution of the spectral line of an OH stretch mode in a hydrogen bonded system as the donor acceptor distance R changes.
Not only does the mode frequency significantly red shift but the spectral intensity, line width and line shape changes significantly.a helpful (short) review from 1991 by S. Bratos, H. Ratajczak, P. Viot
The redshift with increasing bond strength (and decreasing R) is quantitatively described and explained here. I am currently using the same model with collaborators to describe the increase in spectral intensity (by up to two orders of magnitude).
The problem of the line width and the line shape is more difficult and controversial. I discussed some related issues previously here and here.