There is an infinite number of factors you can consider in your decision making process in choosing taking on a project.
In no particular order, here are some of the factors you can weigh when considering:
Quality of project
Variety of project
Gaining experience
Starting relationships
Maintaining relationships
Gaining knowledge
Working in new genres
Having fun
Working out kinks
Practice
Working at new studios
Personal connection to project
Building library
Stretching
Obtaining publishing
Comradery
Pushing out of your comfort zone
Royalties
Fees
Predicted success of the project
Working with musicians
Satisfaction
Who is associated with the project
Fitting into schedule
Building up better precedents
Discovery
Likelihood of earning deferred payment
Getting credit
Adventure
Likelihood of earning bonuses
Prestige of the project
Building reputation
Fulfillment
Exposure
Satisfying curiosity
Ownership
Association with project
Travel
Receiving appreciation
Ego stroking
Impact on perception of you
Excitement
Passion towards the project
PRO earning potential
Staying sharp
Celebrity
Making music
Connection with the filmmakers
Playing multiple roles on project
Helping others
How the project fits into career goals
Soundtrack released
Access
Paying it forward
Award potential
Relieving boredom
Publicity
Blazing new directions
Teamwork
Bragging rights
Premieres
Prestige
Staying relevant
Fame
Contributing art into the world
Musical opportunities within project
Friendships
Taking a challenge
Laughs
Brand building
Honing skills
Residuals
Self satisfaction
Recognition
Experimentation
Personal growth
Opportunity
Creativity
Expression of passion
Connection with others
Appreciation
Joy of risk-taking
Playfulness
Distribution of the project
Artistic expression
WHAT ARE YOUR THOUGHTS ON THIS?
