What does the triangle next to the F in the first bar mean??

Hi Mr Norway.

I'm pretty sure the triangle means major scale/chord or major seventh, so this is another way of saying Fmajor

cheers

Jimu

Yes, it indeed means "major seventh". A common synonym is "Cmaj7". Opposed to "C7" for "minor seventh".

Attached to a minor chord the triangle means the minor-major scale a.k.a. melodic minor.

Ok.

Thanks

What does ø mean then?

It stands for half-diminished, a minor seventh with a flat five. An alternative notation for the same chord is m7b5 For example Eø is the same as Em7b5 and means [E G Bb D].

Hello.

Thanks for a good answer:)

Isn't C7 dominant seventh, and minor seventh notated either Cmin7 or C-7 (or worse yet, Cm7 which is fine if typed but hard to distinguish from CM7 especially if handwritten).

My understanding is that C[triangle]7 is usually paired with C-7 and Cmaj7 with Cmin7 for consistency in a publication.

The intervals are called "minor seventh" and "major seventh". But you are right, the term "C minor seventh" is generally used for a minor chord with a minor seventh. Hence my post before was actually confusing. Sorry for that. I just wanted to point out that the C7 uses a minor seventh extension, as opposed to the major seventh in Cmaj7.