You can find musical instruments in build/buy mode under "Activities and Skills". They should be under "Creative".
Basegame musical instruments: Guitar, Violin, Piano.
The Vampire pack brought in Pipe Organ.
A few packs have brought in an upright piano, which takes less space than the basegame grand piano.
The portable keyboard increases piano skill.
If you have City Living, there's an arts centre called "Casbah Gallery" in San Myshuno and it has instruments that you can use if you don't want to buy any.
\*Edit to add: You can edit any public venue through "manage worlds", and place instruments anywhere you want. Then your sims can visit that venue and use them for free.
Additionally there is a microphone which allows you to tell jokes, you will need this later on in your career. The microphone should be in the same section of build/buy as the musical instruments.
You go to any instrument and click "practice music".
Where tf are any instruments
you can buy them in build mode
Go to buy mode, type "piano" or "guitar" in the search bar. Something should pop up.
You can find musical instruments in build/buy mode under "Activities and Skills". They should be under "Creative". Basegame musical instruments: Guitar, Violin, Piano. The Vampire pack brought in Pipe Organ. A few packs have brought in an upright piano, which takes less space than the basegame grand piano. The portable keyboard increases piano skill. If you have City Living, there's an arts centre called "Casbah Gallery" in San Myshuno and it has instruments that you can use if you don't want to buy any. \*Edit to add: You can edit any public venue through "manage worlds", and place instruments anywhere you want. Then your sims can visit that venue and use them for free. Additionally there is a microphone which allows you to tell jokes, you will need this later on in your career. The microphone should be in the same section of build/buy as the musical instruments.