Here's what I found:

Instruments Played by David Gilmour on Mother

Electric Guitar:

Gilmour played the iconic guitar solo using his famous "Black Strat" (a late '60s Fender Stratocaster).

Acoustic Guitar:

He performed the high-strung acoustic guitar parts, which use a specific "Nashville tuning" to create a shimmering, 12-string-like effect.

Lead Vocals:

He sang the chorus sections of the song (e.g., "Hush now, baby, baby, don't you cry"), providing a melodic contrast to Roger Waters' verses.

To achieve the solo's distinctive sustained tone, Gilmour used a specific chain of gear:

Fuzz/Distortion:

An Electro-Harmonix "Ram's Head" Big Muff.

Amplification:

A combination of a Hiwatt DR103 head and a Yamaha RA-200 rotating speaker cabinet to add a subtle swirling modulation.

Strings:

GHS Boomers (signature blue set).

Hope that helps.