No, you don't need an 88 key piano to be a good musician. In fact, many digital pianos and keyboards have fewer than 88 notes and are perfectly fine for beginners and intermediate players. The important thing is that the keyboard has a weighted action, which simulates the feel of a real piano. So if you're just starting out, don't worry about getting an 88 key piano. Just get one with weighted piano keys, and you'll be fine