Featured Help w/ID George Gershwin Sketch/Portrait

hi everyone. this is a Hail Mary purchase for me. i found this in a Goodwill and i just couldn't put it back. this appears to be an original conte crayon sketch of George Gershwin in profile. it's a nice likeness and it appears to be from maybe the 60s or early 70s. at least that's where i would date the frame(but who knows?). i can not make out the artist's signature(upper right corner). this piece was framed and sold in a gallery in Los Angeles(Charles S. Grieve Gallery). the photos ive provided were taken indoors with my phone. the paper on which the sketch was done is white(the lighting isn't great, but you get the idea). the art is under glass, and i don't want to take the piece apart unless it's necessary. any ideas who the artist is? any help will be greatly appreciated...thanks

 

i forgot to resize the signature picture in the original post. here's a resized pic of the signature.

 

I see 'S Du Sing', but I can't find any artist with that name

 

yes, i was thinking S. Der Sing and found nothing.

 

Dysinger?

 

There is an artist S. Dysinger who does portraits of musicians. Here's information about her and a copy of her signature. (That Calif. abbreviation though may date this to before her time.)

https://www.ebay.com/itm/273591744126

Debora

 

Agree with Debora, Susan Dysinger,(born 1944) and an advert fron Los Angles Times paper has Charles S Greive Gallery still operating from that address in Oct 1965. Also a few examples of her work for sale on various sites from 1970s,so she is most likely to be the artist of your sketch.