MUSIC algorithm for frequency and DOA estimation
The estimation of frequency for one dimensional signal (dimension is time) is same as one dimensional space data for narrow band signal. To make it clear, consider you have n time samples (Nyquist criteria is met) data. The problem of frequency estimation from this n sample is same as the following case. Consider you have a n element linear array (equal spacing) and you have received a time stamp data from a narrow band signal  i.e you have n samples collected at the same time from the n element array. Now once you demodulate or remove the carrier effect from the n samples then the direction finding problem is same as frequency estimation problem mentioned in case of time domain data.

The above is true when there are less then 'n' frequencies present in the signals. Why this is true: the phase difference of the received signal on the array directly related to the angle of arrival. Kindly recall that phase of a sinusoidal is constant.  So time domain data with "fixed sampling frequency" is same as samples on Linear array with equal spacing element(fixed time) after demodulation .

Please understand it is true for narrow-band signal only not broad-band chirp like signal. 

Hope it helps.