Sine Qua Non

Woos. You already got the easy ones.

1. Hardy
2. Sinatra
3. Herbert
4. Capra
5. Stella

Here's 1-1/2:
... Morgan
not so famous today, but ought to be better known:
...[lin] P. Adams

1. enstein
2. Key (i.e. Francis Scott)
3. Valli
4. Gen. Tommy
5. incense

[who is Frank Pippin? I've heard of Scottie Pippen ...]

The easy ones?

Pippin was Charlemagne's father.