Stringed instrument

[j.littleton2]

The flat strip on a stringed instrument where strings lie and can be shortened to produce higher notes

[gen2]

fretboard

[SeaJayPea]

Fingerboard

[rojash]

The generic term "fingerboard" may be applied to both fretted and fretless intruments. Obviously the more specific "fretboard" does not apply to intruments such as the violin, 'cello, fretless bass, etc.

[gastwo]

Fingerboard fits the clue...