spectogram and frequency spectrum values problem

hello all, I would like some help regarding my problem, which is to write a function that takes as input a one-dimensional waveform (a piano signal for this case), and plot its frequency spectrum and its spectrogram. I am not sure if the values I chose are correct and what to do in order to improve the whole thing.

[y,fs] = audioread('pia60.wav');

%sound(y,fs);

S = size(y); %size of y = 125031

Time = length(y)/fs; %duration of the recording

Time

t = [0:length(y)-1]/fs; %the time axis

plot(t,y); %plot the signal

xlabel('seconds');

grid on;

N = 20000;

y1 = y(60000:80000);

fft_vector = fft(y1,N);

m = abs(fft_vector); %we are interested only in the amplitude

x =(0:999)*Fs/N; %the frequency axis with the first 1000 elements

stem(x, m(1:1000)); %plot the frequency spectrum

xlabel ('Frequency [Hz]');

length(fft(y1,N))

%SPECTOGRAM

window = hann(512); %a window with a size of 512 points

noverlap = 256; %the number of noverlaps

nfft = 20000; %size of nfft

spectrogram(y, window, noverlap, nfft, fs)