If you mean like composing music... https://onlinesequencer.net/ This lets you put together a midi with a variety of instruments, it's free and accounts are optional.

Description: | Name: Chris Deadman | Age: 19 | Species: Human | LV: 1 | HP: 15 | ATK: 10 | DEF: 10 | Quiet, analytical, not very expressive, psychopathic? | Asexual, panromantic | Nothing special, really. But maybe he'll be worth something to someone. | \\Lovely base model made by the equally lovely Derp!\\