Assuming that the 9v battery is PP3 size, there isn't any good way to do what you want with the components you have. The motor will probably draw at least 150mA once it gets up to speed, and up to 0.5A under load. At startup it could draw over 2A. The battery will not like this at all.
Here are some typical curves for a PP3 Alkaline battery discharged at 0.5A:-
After 10 minutes at 0.5A the voltage has dropped below 7V (the minimum voltage required for a 78L05 to regulate) which is probably too low for the mic preamp. Furthermore, the high motor motor current could induce noise into the power supply and upset the preamp.
Even if the battery could supply sufficient current to run the motor, the 78L05 regulator can't. You could use an LDO (Low Drop Out) regulator such as the LM2940, but it won't stop the battery from being stressed.
Your motor speed controller is a linear type, which due to its particular design is inefficient at all speeds because the TIP29C transistor is never fully turned on. Whether you connect the speed controller directly to the 9V battery or through a linear regulator the result is the same - most of the limited power available will be wasted.
So how can you get more current at the lower voltage the motor needs, without stressing the battery? The answer is to use a DC/DC converter, which transforms the power from high voltage at low current to low voltage at higher current. Watts = Volts x Amps. A well designed DC/DC converter may be 90% efficient, so if the battery can deliver 100mA at 8V (0.8W) you could get 480mA at 1.5V (0.72W) which might be enough to run your motor and still get reasonable life out of the battery.
Motor speed could be controlled by using a DC/DC converter with variable output voltage. Or you could use your linear speed controller with R2 connected to a higher voltage instead of Vin, which will improve its efficiency because the higher voltage on the transistor's Base will turn it it on harder and deliver full Vin to the motor.
As an alternative to a DC/DC converter you could use another battery (eg. 1 or 2 AA cells providing 1.5 or 3V) to power the motor. This has several advantages:- more power available to the motor, longer run time, and keeps motor noise away from the sensitive microphone amp. You might not like the idea of having to use two batteries, but it is probably the best way to use the parts you have.
Here is an example circuit, which is a modified version of your linear speed controller:-
simulate this circuit – Schematic created using CircuitLab
U1 supplies regulated 5V to voltage divider R2/VR1/R3, which biases Q1. Since the transistor has a current gain of about 50, bias current drawn from the 9V battery will normally be less than 10mA, rising to a maximum of ~40mA when the motor is starting up (limited by R2).
R2 and R3 set the maximum and minimum bias voltages which determine the motor speed range. The values I chose should give a full range from zero to full speed. If you want a more limited range then you can increase their values. You could use a single 1.5V cell if it provides sufficient motor speed, in which case you should increase R2 to 220Ω or higher to reduce the maximum bias voltage.
A separate power switch is not required for the motor battery because when the 9V battery is switched off Q1 won't get any bias voltage, so it will also be turned off.