||:

A

:||:

B

A'

:||

T --->D

D--->T

T--->T

(where T=Tonic; D=Dominant)

I --->V

V--->I

I--->I

(where I=Tonic; V=Dominant)

||:

 Exposition:

:||

 1st theme

Bridge

2nd theme

Closing

I

I--->V or Key 2

V or Key 2

big cadence in V or Key 2

motivic
harmonically stable
homophonic

modulatory
not necessarily motivic
maybe polyphonic

motivic
harmonically stable
homophonic

usually homophonic
maybe fanfare-ish
or motivic references

||:

 Development:

 V or Key 2---> I

"development" of motives from 1st, 2nd, and sometimes Closing themes using fugal techniques of diminution, augmentation, transposition, retrograde, inversion, etc...tends to be more polyphonic than the more homophonic theme sections as a result...very modulatory, that's the point! Melodic sequencing of motivic material very likely during modulation.

Recapitulation:

a repeat of the Exposition with the following important differences

 1st theme

Bridge

2nd theme

Closing

I(as before)

I--->?--->I

I

big cadence in I

 (SOMETIMES NOT IN EXACTLY THE SAME ORDER)

Coda:

:||

literally a "tail", or an extra appendage...strange and new (maybe? you decide)
thematic and harmonic material to re-emphasize the real (this time) final cadence in the I

**

*

from "sonata-allegro form" which designated the form found in every sonata's opening allegro.

**

repeat not always taken–20th-c. performance practice and audiences prefer not to go back to development and recap after strong resolution created by harmonic and thematic return.