I have trouble remembering whether 大 is たい or だい. So, I use custom mnemonics to remember that.
大切: What item of clothes is the most important? Obviously the tie. Having shirts and pants and stuff is nice, but you need a tie to make a good impression.
大学: College is known for being painful, so you could call going to college the “die-study”
大気: You use your superpowers to change the atmosphere, so a tie made out of clouds forms around your neck.
大作: After your epic play is performed, you step out on the stage for praise. However, the first thing you hear is someone shouting ‘Your tie sucks!’ Feel the shock at how rude this heckler is. Feel astonished that they didn’t pay attention to your play.
大会: It’s a tie convention, followed by a tie tournament. How nice does your tie look? How well does it match your suit? How fast can you tie it, and with how little complexity of the knot? This is what you must improve in yourself, to win the tie tournament.
大体: Meaning-The General got to become General generally because he is imposing, he has a BIG BODY. Reading: The General runs up to an enemy, and shouts in his face: ”だい”, and then たいs the enemy in knots.
音楽 using the がく reading is remember thusly: to be any good at music, you must study sound. I know that the 楽 がく is nothing to do with the 学 がく, but the mnemonic is still helpful.