Infrared spectra of the antisymmetric stretching mode ("CN stretch") of the SCN- anion for LiSCN dissolved in the ethers 1,2-dimethoxyethane (1,2-DME), diglyme, triglyme, and poly(ethylene oxide) dimethyl ether of average molar mass 250 (PEO-250) at various concentrations at 25 degrees C reveal that the electrolyte LiSCN is heavily associated to form contact ion pairs LiNCS. A minor amount exists as solvent-separated and/or free ions (Li+S, (NCS)-N-- or (NCS)-N--), the so-called "spectroscopically free" thiocyanate ions. The molecular dynamics of the same electrolyte in the same ethers have been studied by ultrasonic (except for triglyme because of limited solubility of LiSCN) and microwave dielectric relaxation techniques. The ultrasonic relaxation spectra, in the frequency range 1-400 MHz, can be interpreted by the sum of two Debye relaxation processes, which are taken to reflect the multistep Eigen process : [GRAPHICS] Here S is a solvent molecule, whereas O denotes a binding post of the solvent such as an oxygen atom. The fast observed process is attributed to step 2, coupled to the faster step 1, through a pre-equilibration constant K-1. The "slow" observed process is interpreted as due to step 3, coupled with the two faster processes 1 and 2. The interesting finding is that, whereas for 1,2-DME the data follow a separate trend, the data for diglyme and for PEG-250 appear to have the same concentration dependence of both the relaxation times tau(I) and tau(II). Yet, the repetition unit (-CH2CH2O-)(n) number n is 2 for diglyme and 4.6 for PEO-250. For tau(II) vs c(LiSCN), the common concentration dependencies extend to the data in PEO-400. These results are interpreted as meaning that the observed processes, characterized by tau(I) and tau(II), reflect the local relaxation dynamics of desolvation of ions by interchange of the -CH2CH2O- groups by (NCS)-N--, independent of the increase of the chain length of the polyether, within the above range of n values. The UHF-microwave dielectric relaxation spectra of LiSCN in the above solvent systems 1,2-DME, diglyme, and PEO-250 at 25 degrees C and at a concentration C similar or equal to 0.1 mol dm(-3), when coupled with the results of the same spectra for triglyme, reveal a correlation between the solute dielectric relaxation time tau(I)(D) and the repetition number n of the (-CH2CH2O-) units of the polyether. This is taken to indicate that the rotational relaxation time of the solute LiNCS dipoles depends on the chain length of the polyether; namely, tau(I)(D) reflects the long-range dynamics of the solvent.