"A majority of railway commuters reads or listens to music while travelling."

Subject :- A majority of railway commuters

Verb :- reads or listens

Plural subjects take plural verbs so it should be "read" and "listen"

HTH

A majority of railway commuters - plural hence would take plural verb

In this sentence "A majority of railway commuters" is countable and plural

The majority of parliament supports the no confidence motion - here The majority of parliament is non-countable and hence singular

I hope that helps

"Majority" can be either singular or plural

Here it is plural because of railway commuters.

For Eg:
The majority of e-mail users are upset about the increase in spam.

I received a PM asking me to comment.

A number of students play in the band.
A high proportion of students play in the band.
Here, the quantity words in red (A + quantity word) serve to convey the meaning of MANY.
For this reason, the verb is PLURAL.

The number of students is growing.
The proportion of students has grown.
Here, the quantity words in red (THE + quantity word) refer to ACTUAL NUMERICAL VALUES.
A numerical value requires a singular verb:
Five IS a small number.
Two-thirds IS a high proportion.
For this reason, THE number and THE proportion each take a singular verb.

But on the GMAT, the majority typically does not refer to an actual numerical value.
Rather, THE majority -- just like A majority -- simply serves to convey the meaning of MOST.

For this reason, when the majority and a majority refer to COUNTABLE nouns on the GMAT, the verb is PLURAL.
Examples from GMAC:
The majority of successful senior managers do not closely follow the classical rational model.
Among Cheever College students with the best grades, a significant majority take online courses.
The majority of the migrants were motivated by two concurrent factors.
The majority of senior citizens rely entirely on the government pension.
A very large majority of respondents report no change.
The vast majority of false fire alarms are prank calls.
The large majority of scientists have been working in their field for at least fifteen years.
The majority of scientists believe that emissions must be cut.
In each case, the majority/a majority refers to a countable noun and takes a plural verb.

In the entire OG12, I could find only ONE EXAMPLE in which majority serves to refer to a NONCOUNTABLE noun:
The majority of the coal is sold outside the Hazelton area.
Here, the verb (is sold) is singular because the majority refers to a noncountable noun (coal).

Thus, in the vast majority of cases on the GMAT, majority will refer to a COUNTABLE noun and will require a PLURAL verb.

I am realizing that I lack basic grammar and should read grammar books.

this question is about collective noun.

normally, it is sigular
it can be plural to talk about each individual in the group
some cases, it must be plural. "police" is alway plural

read this section of grammar book