I have downloaded two song videos from youtube. I have to join them and make ready for use on stage show of my daughter school program. How do i know that the song would play well. It has to be louder and they will use big speakers. Suggest tool to join and make it ready for the event. The songs are from a TV program and its not available for sale.
closed as not constructive by Breakthrough, Brad Patton, Scott, Renan, Karan May 3 '13 at 16:04
As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance.If this question can be reworded to fit the rules in the help center, please edit the question.
From the information you supplied it's impossible do know what quality the sound has. Generally sound quality on Youtube videos is quite poor as it's more or less compressed. If the source is a third party recording from a TV show I wouldn't be surprised if the quality is pretty bad. Of course it is always depending on what quality the audio had BEFORE the file was uploaded to Youtube.
Then, when downloading a file from Youtube it is important what quality the video has. You can find some more info here: http://www.h3xed.com/web-and-internet/youtube-audio-quality-bitrate-240p-360p-480p-720p-1080p The relevant part of the information found is that videos at 720p and up has decent compression rate (192 kbps). (However many time the source material was recorded or converted at a lower rate and then the higher rate at >720p doesn't matter.)
My advice to you is to try playing the audio in a decent home stereo system loudly and listen to how it sounds.
For combining the sound files the answer provided by r00t_5tr1k3r is sufficient.
Try to use AudaCity. See How to Combine Songs on Your Computer Using Audacity.