I think the physics are always the same, but the trees are different, just like the physics of playing a violin and violoncello is the same but the sounds coming out of them are different. The size and thickness of the tree itself, the size of leaves, the shape of them, the surface of them, the rigidness of petioles and branches - it all makes the difference, makes one tree vibrate a little differently then other trees even of the same specie.

I like the sound of common aspen best, it always reminds me of childhood and summer and just makes me feel good.

The earth is a gargantuous playground for acoustic resonance. Trees and plants and grass and nature in general all vibrate and resonate based on simple yet complex arrangements of acoustic physics. This implies that weight, density, volume, surface area, thickness and etc of a medium all play a role in the sounds that you hear. Nature is a playground for our senses when we care to listen and observe...! 

I would have to agree with mmmm

It just comes down to the shape of the trees, thier height and shape and the shape of the leaves...density of the wood maybe which dictates whether it moves fast in the wind or not.

Books' worth! Any airflow disturbance creates sounds of characteristic volume, frequency, decay, damping, attack, and oscillation. Trees' songs change with wind speed and direction. Higher branches have different shapes and textures of leaves, and encounter higher winds. Thin, threadlike or needle-like leaves or petioles shed vortices as the wind oscillates round them, creating the high-pitched, romantic whisper of conifers. To experiment with the process, whiffle a straightened wire hanger through the air, and compare the effect with the same wire bent into a smooth  scimitar-shape. Then reverse the scimitar, point leading. Its voice suddenly weakens, the vortices flying off alone, instead of trailing along the wire and amplifying new vortices.  Hold threads of various thicknesses under various tensions beside your ear as Aeolian speedometers; you may be surprised at the clarity of their sound even at walking pace.  

Flat leaves flap like flags, depending on thickness, firmness, edge outline, and surface texture. This is commonly the main component of the rustling sound. Pointed, narrow willow leaves shed wind energy with whisperings rather than flappings. Colliding leaves suffer damage, so they grow in patterns that avoid touch, but in high winds impact is inevitable, causing another kind of rustling. Smooth, large, simple leaves tend to give low notes except when flapping vigorously; trees with small or compound leaves, prominent veins, complex outlines, furry surfaces, and rough bark, seem quieter, but they produce more ultrasonics. Crisp autumn leaves act as rattles. Hollow leaves galled by aphids, and swollen Acacia thorns hollowed by ants, may actually whistle. Dense foliage damps the transmission of high notes. The leaves of rushes scrape and vibrate like the reeds of wind instruments; their susurration and sibilation gave rise to the Greek legend about their whispering: "Midas has asses' ears!"

Any airflow disturbance, such as that caused by leaves, creates sounds of characteristic volume, frequency and oscillation. Trees' songs change with wind speed and direction, and the type of leaves.

Needle-like leaves, or petioles, shed vortices as the wind oscillates round them, creating the high-pitched, romantic whisper of conifers. Flat leaves flap like flags, depending on thickness, firmness, edge outline and surface texture. This is commonly the main component of the rustling sound. Pointed, narrow willow leaves shed wind energy with whisperings.

Colliding leaves suffer damage, so they grow in patterns to avoid touch. In high winds, though, impact is inevitable, causing another kind of rustling. Smooth, large, simple leaves tend to give low notes except when flapping vigorously; trees with small leaves, prominent veins, complex outlines, furry surfaces and rough bark seem quieter, but produce ultrasonic sounds.

Crisp autumn leaves act as rattles. Hollow leaves emptied by aphids, and acacia thorns hollowed by ants, may whistle. Dense foliage dampens high notes. Leaves on high branches differ in shape and texture, and encounter higher winds. The leaves of rushes scrape and vibrate like the reeds of wind instruments, giving rise to the Greek legend about their whispering: "King Midas has ass's ears!"

Jon Richfield, Somerset West, South Africa