Would this homebrew college of spirit be unbalanced? What should I change?

I’m currently running a campaign within Ravnica, and one of my player came to me with this homebrew for her bard working within Orzhov guild.

I wanted to be sure first (as I’m a new DM and relatively new 5e player) that it wouldn’t bring problem to the table?

This subclass purpose is to let her play with the Orzhov ghost that are one of the more characteristic trait of this guild in a fun and "bardic" way, which I find quite cool.

This homebrew is not my creation, and neither is the one of my player as she found it on reddit (and tweaked it as she told me the base one was too powerfull).

I’m a new DM, and relatively new D&D player, so I’m not the best at balancing, however:

• I fear that this free cantrip at level 3 might bring unbalance, considering the other bonuses (that are more core to the class)
• I’m not too sure to know what to think about the fear part (don’t see it as too powerful as there is so much resistance to that effect)
• The spirits are ok (need concentration, which should lower their power greatly), even maybe too weak?
• The last ability is too different from what I’m used too so I don’t know what to think of it?

Last Request 3rd-level College of Spirits feature

At 3rd level your music is so alluring to the spirits following you
that you may beseech them for help.

As a bonus action you may expend one of your bardic inspiration dice
and call upon the aid of a friendly specter. When you do so, gain 5
temporary hit points, additionally choose a number of creatures you
can see within 60 feet of you, up to a number equal your charisma
modifier (minimum of one), they must succeed on a wisdom save or be
frightened until the end of your next turn.

In addition, anyone who has one of your bardic inspiration dice can
use a bonus action to expend it on his turn for the same effect, using
your charisma modifier and spell save dc.

The number of temporary hit points increases when you reach certain
levels in this class, increasing to 8 at 5th level, 11 at 10th level,
and 14 at 15th level.

Sounds of Death 3rd-level College of Spirits feature

When you join the college of spirits at 3rd level, you learn to
suffuse your songs and music with the ability to reveal the thin veil
between this world and the next one.

You learn the cantrip toll the dead, to cast it you play a melancholic
tune and through your song reveal its imminent death to the creature
you’re targeting. This count as a bard cantrip for you but doesn’t
count against the number of cantrip you know.

Additionally, you can start a musical performance lasting 10 minute to
attune to the nature of death and learn information on the untimely
demise of any creature within your surroundings, if these creature
died within the last 24 hours. At the end of this recital, roll a
performance check and look in the table below:

• 5: You learn how many creature died in this location within the specified time frame.
• 10: You learn the type of creature that died in this location.
• 15: The time frame increase to the last week, additionally you learn where their body rest (if any and they haven’t been moved
  more than half a mile)
• 20: You learn the nature of the death of the creature within that location within the specified time frame.
• 25: The time frame increase to the last month. But extend past that for any ghost haunting this location.
• 30: You learn the identity of any creature that died in this location within the specified time frame.

Haunting Melody 6th-level College of Spirits feature

Starting at 6th level, you learn the speak with dead spell or choose
a different bard spell of equal level if you already know it. This
does not count against the number of bard spells you know.

In addition, as an action you can start a haunting melody that summons
three friendly spirits to your aid within 60 feet of you. These
spirits last for 1 hour, until they drop to 0 hit points, or until you
stop concentrating on the melody (as if you were concentrating on a
spell). These spirits are friendly to you and your companions and obey
all verbal commands you issue to them (no action required). In combat
these spirits share your initiative count, but take their turns
immediately after yours. However being made of immaterial matter, they
are not able to interact with the physical world, preventing them from
using the help, shove, use object or grapple action.

Once you have called upon these spirits, you cannot do so again until
you finish a long rest.

Lastly, if you are playing your haunting melody directly after your
practicing your sound of death performance, you may cast the speak
with dead spell on the spirits you summoned. Once they answer 5
questions they will vanish, ending haunting melody early, none but you
will be able to hear their answers.

Spectral Resonance 14th-level College of Spirits feature

Starting at 14th level, you have learned to harmonize with the veil
between life and death. As a bonus action you can undergo a ghostly
transformation for 1 minute, until you end it as a bonus action, or
until you are incapacitated. During the transformation, you gain the
following benefits:

• You gain a flying speed equal to your walking speed You can see into
  the Ethereal Plane up to 60 feet away.
• You have advantage on all persuasion checks you make on undead creatures.
• You can use a bonus action to cast etherealness on yourself, without need for verbal or somatic components and without expending a spell slot.
  You may also end this spell as a bonus action. This spell will last only as long as your spectral resonance and doesn’t impede your flying speed.
  Additionally, spirits summoned by your Haunting Melody trait can still
  perceive and interact with you as normal.
• Once you use this feature
  you must complete a long rest before you can do so again.

Let me know if it would seems unbalanced and I’ll see the modification with her.