My advice for remembering instrumental melodies:
Sing them while you practice and also away from
the instrument. I find learning by ear really
helpful. Try to sing 2 bar phrase #1 from a recording, then find
it on your instrument. Do the same with phrase
#2, connect them together, etc. Also notice
how tunes you are learning are similar
to tunes you know. Music jam sessions in pubs
are really good practice for this. I try to define
a tune by phrases & familiar melodic moves, and play
it the second time through (quietly). Reading up on
music theory, especially the concept of "guide tone lines"
can be very helpful. I also practice a lot of
patterns and extend them into unfamiliar places.
Consider: do=1 re=2 etc. try these patterns 321432543654 or 423153426453
etc Also I do a lot of noodling, but with a purpose :^)
Its playing fiddletune type phrases and recognizing
the underlying arpeggio fragments. A nice lick over
a chord incorporates or "approaches" the arpeggio in
some interesting way. You can analyze this if you know
all the notes on your instrument. All these things
I've mentioned serve to build-in flexibility and pattern
recognition. The opposite of this is to rely on what I call
"finger memory" without the "singing voice" being engaged.
Joel Glassman