Circuit design for variable frequency, pure sine wave tone oscillator ~400-1000Hz

I am looking to hire someone to design a circuit for me. The concept is fairly simple: I need a tone generator which produces a pure sine wave signal and drives a speaker at about 1 or 2 watts, so some amplification is needed. It needs to have variable frequency (~400-1000Hz) and volume control via potentiometers. The project is for a Morse code practice oscillator. The sound should be clean and highly responsive with the switching/keying, without any clicking sounds, or transient noise etc. In an 'idle' state there should be no sound produced from the speaker, so one would not even know it is on. Since the device will be portable, power will be provided via some internal rechargeable battery (to be determined) so the lower the power consumption the better.

I am good with PCB layout, so a provable design and schematic with BOM would be ideal.

Thank you!