**For a nine-month-old, I’d start with songs you sing yourself, simple action songs, and a few gentle recordings.** Classical music is an option, but you don’t need a special “baby music” collection.

Your concern about sudden loud passages is sensible. I’d treat “dramatic” as a matter of your son’s reaction, rather than a reason to exclude a whole genre.

Other useful criteria are:

- **Comfortable volume.** Keep recordings quiet enough that you can speak normally over them, and place the speaker away from his head. Overall loudness and listening duration matter more for hearing safety than musical style. [NIDCD guidance](https://www.nidcd.nih.gov/health/protect-your-childs-hearing)
- **Opportunities to interact.** Choose music you can sing along with, sway to, or accompany with gentle clapping. Your familiar voice is a particularly good starting point: babies recognise caregivers’ voices and associate them with comfort. [American Academy of Pediatrics](https://www.healthychildren.org/English/ages-stages/baby/Pages/Hearing-and-Making-Sounds.aspx)
- **Repetition and a clear pulse.** Repeated verses and a recognisable beat make it easy to turn a song into a shared game. These are useful selection preferences, not requirements.
- **A match for the moment.** Try slow, gentle music when settling down and livelier songs during play. Music for an awake, interested baby needn’t all sound like a lullaby.
- **His response.** Watch for smiling, babbling, reaching or moving along. If he becomes upset or loses interest, lower the volume, change the music or stop.
- **Quiet breaks.** Music can be an activity rather than continuous background sound. A noisy environment can make speech harder for young children to understand. [AAP guidance on noise](https://www.healthychildren.org/English/safety-prevention/all-around/Pages/how-noise-affects-your-child.aspx)

Here are some starting suggestions, chosen for their musical character rather than any proven special benefit for babies:

| Music | Why try it? |
|---|---|
| **“Twinkle, Twinkle, Little Star”** or **“Row, Row, Row Your Boat,”** sung by you | Short, repetitive melodies; easy to sing softly and pair with swaying |
| **“The Wheels on the Bus”** or **“If You’re Happy and You Know It”** | Repeated verses and gestures for shared play; increasingly useful as he becomes a toddler |
| **Bach: Prelude in C major, BWV 846**, on piano | A flowing, repeating accompaniment pattern |
| **Satie: Gymnopédie No. 1**, on piano | Slow and spacious |
| **Saint-Saëns: “The Swan”**, for cello with piano accompaniment | A smooth melody with flowing accompaniment |
| **Softly performed folk songs or acoustic songs you enjoy** | A way to introduce variety while singing or moving together |

**Preview the actual recording**, including its loudest passage: arrangements and performances can differ considerably.

There’s no need to favour Mozart for intelligence benefits; research does not establish that playing Mozart to babies raises their IQ. [Harvard’s review](https://news.harvard.edu/gazette/story/2000/10/arts-to-smarts-link-overblown-researchers-sing-a-new-tune-for-the-mozart-effect/)

For your son, try one or two songs while sitting together, repeat whichever catches his interest, and follow his lead. You don’t have to sing well to make that enjoyable.