Uploading Issue - Access Is Denied

Working on a science project of a "Banana Piano" using the Arduino Uno and Scratch software. To use Scratch, it is necessary to upload a Firmware update to the Arduino, which we were able to do. Then we typed in a code so that the speaker that came with the Arduino board would be programmed as an output. When we go to upload this sketch, get the error message below. Tried the troubleshooting guide as well as resetting - when reset, could upload the sketch, but then had to upload the firmware for S4A (Scratch for Arduino) - and then could not make the speaker work. Here is error message; appreciate any suggestions. Thanks!
Arduino: 1.8.5 (Windows 10), Board: "Arduino/Genuino Uno"
Sketch uses 2640 bytes (8%) of program storage space. Maximum is 32256 bytes.
Global variables use 32 bytes (1%) of dynamic memory, leaving 2016 bytes for local variables. Maximum is 2048 bytes.
avrdude: ser_open(): can't open device "\.\COM3": Access is denied.

That means some other program on your computer is using the serial port. Tell it to disconnect or exit that program.

Thank you:)