 Here is a simplified example of how you might structure your code using the BurnMan library. Please note that this is a basic example and might need adjustments based on your specific requirements.

```python
from burnman import EquationOfState, SeismicTable, ClassA_for_copy_documentation
import numpy as np
import matplotlib.pyplot as plt

# Define minerals
olivine = ClassA_for_copy_documentation('olivine', 'forsterite')
pyroxene = ClassA_for_copy_documentation('pyroxene', 'enstatite')
clinopyroxene = ClassA_for_copy_documentation('clinopyroxene', 'diopside')
garnet = ClassA_for_copy_documentation('garnet', 'pyrope')

# Define compositions
olivine_comp = {'Mg#': 0.85}
pyroxene_comp = {'Mg#': 0.85}
clinopyroxene_comp = {'Mg#': 0.75}
garnet_comp = {'Mg#': 0.85, 'Fe#': 0.15}

# Define simple mole fractions
simple_mole_fractions = [(0.5, olivine, olivine_comp), (0.5, pyroxene, pyroxene_comp)]

# Define a mix of three minerals
three_minerals = [(0.4, olivine, olivine_comp), (0.4, pyroxene, pyroxene_comp), (0.2, clinopyroxene, clinopyroxene_comp)]

# Define a preset solution
preset_solution = ClassA_for_copy_documentation('preset_solution', 'olivine_85_pyroxene_85_clinopyroxene_75')

# Define a custom solution
custom_solution = ClassA_for_copy_documentation('custom_solution', 'olivine_85_garnet_85_15')

# Instantiate minerals
olivine_inst = instantiate_minerals(olivine, olivine_comp)
pyroxene_inst = instantiate_minerals(pyroxene, pyroxene_comp)
clinopyroxene_inst = instantiate_minerals(clinopyroxene, clinopyroxene_comp)
garnet_inst = instantiate_minerals(garnet, garnet_comp)
preset_solution_inst = instantiate_minerals(preset_solution, None)
custom_solution_inst = instantiate_minerals(custom_solution, None)

# Set compositions and state from parameters
for mineral, composition in [(olivine_inst, olivine_comp), (pyroxene_inst, pyroxene_comp), (clinopyroxene_inst, clinopyroxene_comp), (garnet_inst, garnet_comp), (preset_solution_inst, None), (custom_solution_inst, None)]:
    mineral.set_compositions_and_state_from_parameters(composition, pressure=100000, temperature=1500)

# Compute seismic properties
Vs, Vphi, density, geotherm = test_seismic(mineral_list=[olivine_inst, pyroxene_inst, clinopyroxene_inst, garnet_inst, preset_solution_inst, custom_solution_inst], pressure=np.logspace(0, 10, 1000))

# Define seismic reference model
reference_Vs = np.array([1.8, 2.0, 2.2, 2.4, 2.6, 2.8])
reference_Vphi = np.array([0.8, 0.9, 1.0, 1.1, 1.2, 1.3])
reference_density = np.array([3.3, 3.5, 3.7, 3.9, 4.1, 4.3])
reference_geotherm = np.array([1000, 20000, 40000, 60000, 80000, 100000])

# Calculate misfit
misfit_Vs = np.abs(Vs - reference_Vs)
misfit_Vphi = np.abs(Vphi - reference_Vphi)
misfit_density = np.abs(density - reference_density)
misfit_geotherm = np.abs(geotherm - reference_geotherm)

# Plot results
fig, axs = plt.subplots(4, 2, figsize=(12, 18))
axs[0, 0].plot(geotherm, Vs, label='Computed')
axs[0, 0].plot(reference_geotherm, reference_Vs, label='Reference')
axs[0, 0].set_xlabel('Pressure (GPa)')
axs[0, 0].set_ylabel('Vs (km/s)')
axs[0, 0].legend()

axs[0, 1].plot(geotherm, Vphi, label='Computed')
axs[0, 1].plot(reference_geotherm, reference_Vphi, label='Reference')
axs[0, 1].set_xlabel('Pressure (GPa)')
axs[0, 1].set_ylabel('Vphi (km/s)')
axs[0, 1].legend()

axs[1, 0].plot(geotherm, density, label='Computed')
axs[1, 0].plot(reference_geotherm, reference_density, label='Reference')
axs[1, 0].set_xlabel('Pressure (GPa)')
axs[1, 0].set_ylabel('Density (g/cm³)')
axs[1, 0].legend()

axs[1, 1].plot(geotherm, misfit_Vs, label='Vs Misfit')
axs[1, 1].plot(geotherm, misfit_Vphi, label='Vphi Misfit')
axs[1, 1].plot(geotherm, misfit_density, label='Density Misfit')
axs[1, 1].set_xlabel('Pressure (GPa)')
axs[1, 1].set_ylabel('Misfit')
axs[1, 1].legend()

plt.savefig('seismic_properties.png')
plt.show()
```

This code creates several minerals, sets their compositions, computes seismic properties, and compares them to a seismic reference model. It also calculates the misfit between the computed and reference values and plots the computed and reference values of Vs, Vphi, density, and geotherm against pressure. The plots are saved as an image file named 'seismic_properties.png'.