Possible Clues:

• Jimi Hendrix classic
• Classic rock hit that asks 'Is it tomorrow or just the end of time?'
• 1967 hit whose title is sung before "all in my brain" (... 7- and 23-Down)
• #2 on Rolling Stone's '100 Greatest Guitar Songs of All Time'
• Psychedelic rock classic of 1967
• What's 'all in my brain,' in a 1967 rock classic
• Song by 56-Across