My first sound is found when half isn’t around.
When a pair is amiss, the other is called this.
The second has one, where normally two form a pair.
You will get the nod if you look in a pod.
Together, my fifth and third hold music that is heard.
A pair you are seeking, alphabetically speaking.
Expediency (XPDNC)
The five letters, XPDNC, sound just like the ten-letter word expediency.
After a divorce (a couple is amiss), the former partner is called an ex (X).
Normally there are two peas in a pod, but here we just want one pea (P).
C and D are beside each other in the alphabet, and together hold music as a CD.
In the middle of END is the letter N.